Wilfrid Sellars*

Published in Philosophy for The Future, The Quest of Modern Materialism, edited by Roy Wood Sellars, V.J. McGill, and Marvin Farber (New York: The Macmillan Co., 1949): 544-70.

I propose in this essay to examine certain concepts and propositions which make up the backbone of the Aristotelian philosophy of mind. Since I do not have the space to develop my argument by way of detailed commentary on texts and quotations, and since isolated quotations are notoriously two-faced and of little scholarly value compared to the space necessary to make them intelligible to the non-technical reader, I shall instead proceed by developing as clearly as possible the assumptions and conclusions which, as I see it, are typical of the way in which classical Aristotelianism dealt with problems relating to the nature of thought. By laying bear its logical skeleton, I hope to show how reasonable the Aristotelian philosophy was, and that, in so far as it made mistakes, the mistakes were not foolish but sprang from plausibilities and confusions the true character of which could be exposed only with the aid of intellectual tools which were centuries in the future, and are not even yet in general use among philosophers.

Before we turn to this more specific task, however, we must first [545] sketch the general framework of ideas in terms of which this philosophy approaches its problems. The framework is the hylomorphic conception of the world; that is to say, its interpretation in terms of the contrast between matter (hyle) and form (morphe) as these terms are understood in the Aristotelian tradition.1

At the level of common sense we interpret our world as consisting of an immense multitude of things each of which falls in one or another of a relatively small number of kinds. These things work out histories consisting of successive states. Though things and states alike come into existence and cease to exist, things are distinguishable from their actual histories. This difference is bound up with the fact that a thing could have behaved otherwise than it actually did. The "capacities" of things are richer than the actual sequence of events in which they participate. Though this water is now liquid, it could have been solid; it had it in it to be solid. What a thing has it in to be is its nature. It is the nature of water to freeze and boil; of turnip seeds to grow into turnips. It is with reference to their natures that things are divided into kinds.

Something is clearly lacking in what I have just said. We must say not only that a thing could have behaved otherwise than it did, but also that it would have behaved differently if the circumstances had been different. Water is not only "capable" of freezing ; it would freeze if the temperature were reduced to 32° F. To clarify this fact we must distinguish between the concepts of capacity and dispositional property.2 Both involve a reference to laws of nature, but the former is a weaker notion and is essentially negative. To say that a thing is capable of being in a certain state is to say that its being in that state is contrary to no law of nature.3 On the other hand, to speak of a dispositional property of the thing with respect to that state involves a positive reference to a law associating that state with a certain kind of circumstance. Thus, to say that dispositional property D necessitates the occurrence of state Si in circumstance Ci must, if true, be true by definition; for D can only be defined as the
property of being in state S1in circumstancesC1
S2 C2
. .
. .
Sn Cn
and, if the statement is true, then Si and Ci must be among the values included in these lists.

Now while the above indicates the lines along which the concept [546] of a dispositional property and hence of the nature of a thing would have to be analyzed and already makes it clear that the correct analysis of what a thing has it in it to be involves a reference to causal laws, it is by no means true that one must know this analysis in order to make use of the thing-nature language. It is characteristic of human thought that we are constantly making sensible use of concepts which we are not able, at the time, to explicate.

It follows from what we have been saying that concepts of kinds of things are the ways in which common sense crystallizes its experience of the world, and that this crystallization contains the common-sense grasp of natural laws, crude and incomplete though this grasp may be. To the philosopher it is an interesting and important fact that common sense thus formulates its understanding of the world order in terms of a framework which, when correctly analyzed, is seen to be logically more complicated than that of a functional correlation of events.4 It is not my purpose either to "defend" or to "attack" the thing-nature framework,5 but rather to show the use to which it was put by a philosophy which was unable to give it a correct analysis.

I conclude, then, that the concept of the nature of a thing, in so far as it is a coherent one, can be analyzed in terms of the concept of dovetailing set of dispositional properties which specify both the states by which it has responded to its historical circumstances, and the states by which it would have responded to other circumstances.

We have spoken of a "dovetailing set of dispositional properties," for it is clear that according to the common-sense framework, a thing not only may, but invariably does have more than one dispositional property. Of the relations between different properties (we shall now use this shorter expression) of one and the same thing, that which most interested the Aristotelians was a relation which we might call "being founded on." Thus, to the Aristotelian, biological properties are founded on physico-chemical properties. This relation is not to be confused with that of being analyzable into, which is what the mechanist believes to hold in the case of these kinds of properties.

According to the Aristotelian, the various kinds of things to be found in our part of the universe fall into irreducible levels. The hierarchy consists of (1) merely physical substances, (2) living but not sensate physical substances (the vegetative level), (3) sensate but not rational living physical substances (the brute level), and (4) rational sensate living physical substances. Each thing or substance of a higher level has properties of a kind to be found in things of a lower level. [547] Thus, vegetables fall, animals take nutriment, and men have the power of sensation.

The Aristotelian also insists that the lower level properties of higher level substances are not identical with the lower lever properties of lower level substances. This is reasonable, since, for example, what physical events will happen to a higher order substance, e.g. sensations and appetites, are going on in that substance.6 The lower order properties of higher order substances are thus as bound up with the higher order properties of these substances as the higher order properties are bound up with them.

To sum up, the "dovetailing" of the properties of a substance involves (1) the dependence of higher level properties on lower level properties, (2) the connectedness of its lower level properties with the higher level properties founded on them, and (3) the necessary coexistence of such properties as are on the same level. These three modes of connectedness make the nature of a genuine unity. The concept of unity of the nature of a substance plays a key role in one of the arguments we shall be considering below. Needless to say, all these modes of connectedness can be given a correct analysis only in terms of laws of nature.

We are now in a position to characterize the Aristotelian conception of form. First, we note that it is only too easy to overlook the fact that a disposition word is properly defined in terms of a specific correlation of states and circumstances. One who philosophizes on the basis of the common-sense view of the world has nothing to protect him from thinking of it as standing for an entity which "generates" or "produces" states S1 . . . Sn in circumstances C1 . . . Cn, from finding here an ontological fruitfulness, an overflow, a necessity which is no mere consequence of a definition.7 It is equally easy to fall into the similar error of thinking of the unity of the dovetailing properties which make up the nature of a thing or substance as itself a distinguishable entity from which the various properties "follow" in the same fruitful way.8 Such an entity would be an Aristotelian form, or, as the Scholastics were to put it, substantial form, if the Aristotelians had started out with a reasonably clear-cut notion of a dispositional property and had only blundered in the two ways we have just pointed out. Actually, as we have indicated, they did not have this clear-cut notion. The consequences for the Aristotelian interpretation of nature and science were enormous.

Turning now to the Aristotelian concept of matter, we must be [548] extremely brief, since this concept plays a minimal role in our argument and what must be said can best be said when needed.

We tend today to mean by "matter" a set of things which in no sense are made up of other things, and of which all the properties are of a sort which we should call "physical," or, at least, would refuse to call "mental" or "vital." In this "thing-language" framework, materialism is the doctrine that all things either are "ground-floor" things of the above sort, or else are "made up" of such things. Materialism takes two forms: (1) reduction materialism, according to which all properties of "composite" things are "reducible" to properties of matter -- which amounts to saying that except for convenience (abbreviation) an omniscient scientist would need no more non-logical and non-mathematical symbols to describe human organisms than he needs to describe the behavior of matter in a mindless universe. I say "behavior" because if dispositional properties are included, the criterion will not distinguish reductive from non- reductive materialism. For if reductive materialism be false, one would not describe the dispositional properties of matter in a mindless universe without referring to specifically mental characteristics. (If such and such had happened, mental events would have occurred, and the universe would not have been mindless.) (2) Emergent materialism is materialism which denies the "reductionist" claim.

The notion to be found in emergent materialism of things and properties which are "founded" on "lower level things and properties" and ultimately on "ground-floor things and properties," is also to be found in Aristotle;9 and when he says that matter is matter for form, part of what he has in mind is that lower order things are matter for higher order things which, in some sense, include them without being reducible to them. It is only with the further contention that even ground-floor substances consist of matter and form that the Aristotelian conception of matter shows itself to be radically different from that of the emergent materialist. That ground-floor substances involve form is clear; water (which is one of Aristotle's ground-floor substances) has a nature, has properties. But what could the matter for water be? Clearly it cannot be a substance with a nature, for then water would not be on the ground floor. Thus, the "matter" for ground-floor substances must be "indeterminate," that is to say, without a positive nature of its own.

Why did Aristotle think that he needed an indeterminate principle? There are a number of mutually reenforcing considerations, some of [549] which will come out in our later argument. At this point we shall limit ourselves to pointing out that Aristotle, in accordance with what was rapidly becoming the dominant trend in classical philosophy, refused to think of the actual history of the world as an ultimate fact. Process must not only depend on, it must also somehow be derived from factors which are intrinsically immune from change or becoming. (It will be recognized that this assumption underlies many of the metaphysical arguments for the existence of God.) Now, things or substances change; but it does not even make sense (except metaphorically) to say that the natures or forms of things change. Thus, change is impossible unless there is more to things than their forms. This more is matter, prime or first matter. But not all forms need matter; only those from whose forms "follow" contrary states, only those whose nature involves a reference to states which cannot coexist -- only the forms of changing things.

How matter which is completely indeterminate can cooperate with form to "produce" change, or how, indeed, it can perform any function, is difficult to see, though we shall have more to say on this subject later on. The inadequacy of form and matter to "account" for change is recognized by Aristotle himself; he finds himself forced to introduce an Unchanging Changer. But it is, of course, no easier to "derive" change from three unchanging factors than from two. The actual history of the universe must be recognized to be an ultimate fact. There may be other aspects of reality on which process depends, in the sense that without them it would be impossible; but process cannot derive from that which is not process. This, however, is a story for another occasion.


In the Pre-Socratic period of Greek philosophy, philosophers had searched for one or more stuffs of which all things are made. Thus if they spoke of the "common realities" shared by the objects of our sense experience, they meant the ultimate ingredients of which perceptible, ephemeral objects were mixtures. Socrates and Plato, on the other hand, gradually and imperfectly disentangled the different notion of the common as universal.

When today the philosopher considers the statements, "This is a triangle" and "That is a triangle," he characterizes them as saying of two particulars that they exemplify one and the same universal, namely Triangularity, and he does this irrespective of his views on the "ontological status" of universals. Thus, in interpreting these statements, he characterizes Triangularity as an identity which is [550] common to the many triangular objects that come and go in the world process.

Now it is clear that it does not make sense to speak of universals as changing or coming into existence or ceasing to be. It is rather to the objects which exemplify universals that these concepts apply. In these respects, universals are like the fundamental stuffs of the Pre-Socratics, for example the atoms of Democritus.10 If it is pointed out that the latter were not immune from all change, since they formed the world-process by a constant mixing and unmixing, can we not reply that the various universals are related to (exemplified by) different particulars at different times? This point of resemblance between universals and world-stuffs might have been sufficient by itself to lead Socrates and perhaps the younger Plato to hold that universals are ingredients, and, indeed, the most real ingredients of the world-process. But there were other and even more convincing considerations.

Every truth (or falsehood, for that matter) involves at least one universal. Thus, "This is round" tells us that in this we have a case of Roundness, that this exemplifies Roundness. Now thoughts, or at least some kinds of thought, are characterizable as either true or false. Therefore thought has to do with universals. It is difficult (though, fortunately, not impossible) to avoid the conclusion that this is no metaphor. Surely universals must have a mode of existence such that mind can "grasp" or "apprehend" them.11

Thus, universals became to incipient Platonism the most real ingredients of the world-process, which thought could grasp, thus gaining knowledge of existence in so far as it is capable of being known. Furthermore, thought at its best, which, for the Greeks, was the thinking characteristic of geometrical demonstration, not only is concerned with universals (the various kinds of geometrical object) but is actually indifferent as to whether or not these universals are exemplified in the "world of becoming." Universals, it was concluded, are the appropriate objects of mind; particulars are the appropriate objects of the senses.12

It soon became apparent that the relation of universals to perceptible objects was quite different than that of the atoms or other elemental ingredients discussed by the Pre-Socratics. "Mixing" and "sharing" or "participation" could now be used only in a thoroughly [551] metaphorical sense. Yet that the spatio-temporal world is in some way derived from a domain of universals (perhaps in conjunction with an equally ultimate but amorphous principle), and that knowledge at its best consists of a "vision" or "grasping" of these universals, -- these are enduring elements in the Platonic tradition. Just how the relation of universals to particulars was to be understood became a serious problem. Fortunately, the history of this problem does not concern us here.


Let us approach the Aristotelian-Thomist theory of mind in terms of the place of the senses in the human cognitive enterprise. We have already pointed out that, for Plato, thought at its best is solely concerned with the Ideas and their mutual relationships and, in this respect at least, is independent of the senses. Yet, even though one holds that thought at its best is not directed upon the objects of perception, there is room for maintaining a causal or generic dependence of even such thought on sense experience and imagination. In other words the shifting progress of thought by which we "grasp" now one universal, now another, may rest, in whole or in part, on the stream of sense and imagery -- by which a reciprocal influence is not excluded.

One possible view would be that sense-experience (including the imagination) completely determines the subject matter of thought, in the sense that it "selects" the universals to be "grasped" by thought. Such an approach is completely foreign to Platonism. It is only if one is convinced on "a priori" grounds that thought must be paralleled by experienced or imagined objects that one finds the courage to populate the imagination with non-linguistic counterparts of thought. (To the empirically minded, of course, the only sensuous items which parallel the course of thought so closely that they could with some plausibility be held to be its determinants, are the symbolic or linguistic activities of the imagination which the Platonist, when he notices them at all, takes to be a consequence or "expression" of thought. (It is these symbol activities which the contemporary anti-Platonist identifies with thought. They are organic functions of much greater "depth" than the mere occurrence of verbal imagery.) The fact that classical philosophy neglected or minimized the role of symbolizing activities in its interpretation of thought is of vital [552] importance for the argument that follows. We shall not have these activities in mind unless we explicitly mention them. Thus, unless otherwise indicated, they will be excluded from the scope of the terms "sense" and "imagination."

Now, while Aristotle, in common with Plato, rejects the position that the data of the senses and the imagination are the sole cause of the course of thought, he nevertheless insists, and in so doing parts company with Plato, that sense or imagination is a necessary condition of every thought in that no universal13 can be apprehended unless an instance of that universal is given to sense or imagination.14 We shall be concerned to draw out the implication of this position, for we shall discover that the characteristic features of the Aristotelian theory of knowledge, including the puzzling distinction between the "agent intellect" and the "possible intellect," can be traced to Aristotle's adoption of this alternative.

In order to understand the development of the Aristotelian theory of knowledge, one must appreciate the extent to which mathematics and, in particular, geometry dominated the intellectual scene in antiquity. Geometry, it must be borne in mind, was conceived of as a science which begins with infallibly grasped elementary truths about elementary geometrical objects, and proceeds to derive complicated truths concerning complicated geometrical objects. Thus conceived, geometry was a set of apprehended necessary connections between geometrical kinds (Point, Line, Triangle, etc.) forming a tight system with a foundation of self-evident first principles. In the absence of systematic empirical science (e.g., physics as we know it) the Greeks tended to draw the boundary between general truths which were knowledge or science, and general truths which were educated guesses ("mere" opinion) in such a way that science included only mathematics. Today, on the other hand, while we should not regard empirical science as identical in either method or the status of its results with pure mathematics, we should include both the boundary which marks off reliable knowledge or science from the rule-of-thumb beliefs of common sense.

One of the characteristic features of classical geometry was the fact that its objects were capable of being given, even if only "imperfectly," a sensuous embodiment. Our visual field, in particular, [553] presents us with geometrical points, lines, planes, and solids, as the boundaries of qualitative differences -- a line, for example, being a boundary between two adjacent color expanses. Furthermore, mathematicians made use of this fact in developing their proofs; and while it was recognized that the proofs were not about the particular lines in the diagram, yet it was believed that scrutiny of the construction was essential to the grasp of the demonstration. That this is not true of properly formulated Euclidian demonstrations (such as now exist), the theorems being logically contained in the premises, is not to the point. The historically significant fact is that there was sufficient misunderstanding of the nature of geometrical argument for it to be believed that scrutiny of diagrams is an essential ingredient in proof.

Turning now to Plato, we find him insisting on the necessity of diagrams for geometrical reasoning.15 We might, therefore, be prepared to find him insisting that in all scientific thought there must be "illustrative material" to play the role played by diagrams in geometry. However, in the very passage in which he insists that diagrams are necessary to the geometer's thinking about geometrical kinds, he points out that the philosopher or dialectician has no need of diagrams for his thinking about geometrical or other kinds. We do not find in Plato a doctrine to the effect that to grasp an idea we must be acquainted at the time with an experienced exemplification of that idea.16 On the other hand, whether it is because universals exist only "in" particulars (which is therefore "where" to apprehend them) or because universals are natures of experienced particulars which take on the character of universality for thought (so that in the absence of an experienced -- or imagined -- particular there can be no universal-for-thought), the Aristotelian insists that a universal can be grasped only by a mind which is acquainted at that time with a sensed or imagined exemplification of that universal. This notion, together with an un-Platonic optimism concerning the possibility of a science of the "world of becoming" (in the classical sense of "science" which we characterized above), led to the characteristically Aristotelian conception of the sciences of nature and man.

This conception, absorbed by Aquinas, and only gradually questioned by later Thomists under the impact of modern science, can be called the "abstractive theory of scientific knowledge." According to it, a truly scientific understanding of the various kinds of object in the world of nature is achieved by abstracting the forms of these objects from experienced cases, just as (supposedly) a truly scientific [554] understanding of geometrical shapes is achieved by abstracting geometrical natures from experienced cases. Scientific method is that which conduces to the grasping of an ordered manifold of truths about a kind of object, by bringing about the grasping of the substantial form of an object of that kind -- which substantial form is, as we saw above (p. 547. see also note 8), the ontological source of these truths. The fundamental role played by sense in this process is that of providing experienced cases from which the form is abstracted.

Aristotle combined his "abstractive" theory of thought with a causal theory of sense-perception. By this I mean that, for him, the contribution of the senses to experience consists in the fruit of the action of external objects on the organs of sense. This action was said, in Scholastic terminology, to "impress" the "sensible species" or "sensible form" of the object (e.g., a lion) on the organs of sense17 -- "sensible forms" seeming to mean the states (or powers) of the object to which are due the resulting states of the sense organs affected by the object. The analogy used by the Aristotelians is that of a signet ring impressing its shape on wax. It is the sensible form of an object as "impressed" on the perceiver which is conceived by the Aristotelian to be the basis of an abstractive science of the object, as boundaries in the visual field are the basis of an abstractive geometry of the shapes of physical objects.18

Let us now ask the question, "How must the impressed sensible form of a lion be related to the substantial form of the lion if it is to be the basis for an abstractive science of lions?" Clearly, since the abstractive science of lions is the grasping of what flows from the ontological richness of the substantial form, and since the substantial form is abstracted from the perceptions of the senses, this form (called in the context of knowledge the "intelligible form") must be present in the impressed sensible form.19 Here a decisive difficulty arises. Must we not say that for the senses to have impressed on them a character which includes the substantial form Lion, is for the senses to exemplify this form, and hence to become or contain a lion? (So that one who sees a lion would literally have a lion in his eye!)

There would seem to be only two ways out of this difficulty if the notion of an abstractive science of lions is to be retained. (1) The causal theory of perception might be abandoned in favor of a direct realism. Lions are directly apprehended, and the intelligible form is abstracted from the lion, and not from the product of the lion's action [555] on the eye. Whatever might be said for or against such a theory, it is not to be found in either ancient or medieval philosophy -- while modern direct realism has no truck with the abstractive theory of science. (2) The intelligible form might be held to be in the sense organ, but not by way of actual exemplification. Lion would have existence for sense, as opposed to actual existence, in the impressed sensible form. Two comments can be made on this suggestion which is to be found, for example, in Brennan's Thomistic Psychology, p. 117 (see also pp. 112 ff., 135-137; Maritain, The Degrees of Knowledge, p. 140). (a) To speak of the "existence for sense" of a lion when a tawny sensation occurs can at best be a misleading way of pointing out that the process of sense perception involves interpretation or thought in addition to mere sensation. Thus, "existence for sense" when it is opposed to "actual existence" is just a special case of "existence for thought". If this is so, then the "presence" of the intelligible form in a perception can hardly be that from which the thought of the intelligible form is derived, since it is that thought itself (albeit on an unreflective level). (b) Even should it be insisted that "existence for sense" is to be distinguished from both "actual existence" and "existence for thought." the result would merely be that the abstractive theory of thought would be explaining our ability to think of something (give it existence for thought) in terms of an ability of the same general kind (our ability to give things existence for sense) which is taken as ultimate. It is clear that the abstractive theory of thought makes sense only as a theory to the effect that the thought of, say, Triangularity is abstracted from an actual case of Triangularity.

The conception of natural science as a matter of abstracting intelligible forms from impressed sensible forms is, of course, of merely historical interest. Before we go on to see what has taken its place in recent Thomistic thought, let us consider for a moment what is was that made this conception plausible. First, there is the fact that the common-sense view of natural objects, which, since it is a crystallization in language and action of funded human experience, seems bodily given to us by our senses, was essentially all there was to the science of the day. Secondly, there was the complete neglect of linguistic and, in general, symbolic activities and habits in the interpretation of the facts of thought. Thirdly, an anti-Platonistic attitude towards universals, combined with the recognition that thought "deals with universals", led to the abstractive theory of thought. Fourthly, the Aristotelians, lacking the concept of a law of nature, had no clear theoretical understanding of a dispositional property. They did not [556] distinguish it from the weaker notion of a capacity; nor did they have a clear idea of a dispositional property. Consequently, they fell back on pictorial thinking (although in many contexts their statements about properties are quite reasonable!), taking the "potential" to be that which is implicit in a thing, and the implicit to be that which is present in the thing but "obscured by" or "immersed in" matter. Fifthly, instead of thinking of the growth of a living thing (e.g., an acorn) as involving the appearance in an irreversible order of new dispositional properties, and of the nature of a thing as involving the higher order dispositional property of having specified lower order dispositional properties in specified circumstances,20 the confusions mentioned under "fourthly" led them to think of the nature of a thing as an ideal state of the object present in it but obscured by matter, and of growth (which was the ultimate model for their conception of all change) as the progressive increase in the "clarity" with which the ideal stands forth. It is in the context of growth that we best understand the Aristotelian identification of matter with potentiality. In general, we must say that the plausibility of the abstractive theory of science rested on the extent to which lack of clarity in the analysis of the nature of a thing was balanced by a lavish use of matter as an objective unclarity of things, as an ontological bog or mire. As soon as the concept of law of nature as a functional correlation of events came on the intellectual scene, the abstractive theory of science was doomed.

Among contemporary Scholastics, those who have made a sincere effort to interpret the methods and results of modern science (Jacques Maritain and Mortimer Adler, to mention two whose writing are available in English), while they still insist that it makes sense to speak of grasping the intelligible forms of substances, admit that human beings cannot arrive at the intelligible forms of natural substances by abstraction from the perceptions of the senses.21 They admit that empirical science works rather by the method of saving the appearances. But in their interpretation of this method they swing to the opposite extreme, and make the same mistake as the phenomenalists and positivists.

The mistake consists in hanging on to the fundamental thesis of the abstractive theory of thought, as well as to the idea that the data of the senses are the abstractive base of scientific thought, while [557] recognizing that these data do not "contain" substantial forms to be elicited by thought. Thus, these Neo-Thomists regard scientific concepts and propositions as constructions of which the content consists of universals abstracted from the immediate data of the senses, while the rest is a matter of logical and mathematical structure. The importance of "merely symbolic thinking," of language as a calculational device, is discovered and emphasized, though it is insisted that there is also"real thinking" in which the mind is apprehending universals and meanings.22 These New Schoolmen, then, agree with the positivists that, from the standpoint of the philosopher, scientific activity consists in the logical and mathematical manipulation of expressions which stand for actual of possible observations ("Red flash seen . . ." "Arrow-shaped line coincides with dot . . ."), a manipulation which, when successful, enables us to predict (or postdict) the course of sense experience. Those scientific terms which are neither purely logical nor purely mathematical, and do not stand for observable qualities -- in short, those terms which the realistic philosopher of science takes to refer to properties of physical systems -- are interpreted as merely calculational devices, since it is held, in accordance with the abstractive theory of thought, that only those non-logical and non-mathematical terms which name sense qualities name universals at all, given that only these universals can be abstracted from the experiences which are the raw material of empirical science.

Since, after all, these Neo-Thomists are Realists and not Positivists or Phenomenalists, they are led to distinguish between an angelic science which grasps the intelligible forms of things, and human science which builds up, by inductive methods, complex constructions of practical and predictive value.23 Human science, thus systematizes the appearances beneath which there is a core accessible only to the angels. Scientific laws are not truths about the physical world, but are merely calculational devices for predicting sense-experience. Where the Neo-Thomist does not overlook the fact that properties and, indeed, substantial forms can be defined in the language of empirical science, he is forced to hold that such properties and substantial forms are ontologically bogus, substitutes (with a "foundation" in things) for the real article.24 Since the "real" articles they have in mind are only the common-sense notions of the natures of things, the Neo-Thomists are opposing the crystallizations of pre- scientific experience (which has no privileged source of information, and in which time takes place of method) to the fruits of the systematic exploitation of the same material which is empirical science. Or can it be that [558] pre-scientific experience has a privileged source of information? For these philosophers, being uneasy about the extent to which they have trodden the road to phenomenalistic skepticism, hasten to insist that, since "man is of all natural things the one with which man is most intimately acquainted, the only one whose specific nature he is able to comprehend fully," we have in the science of man "the only body of philosophical knowledge relevant to a species of physical thing."25 Here alone can abstractive thought with ontological, as opposed to merely phenomenalistic, reach supplement the constructions of empirical science. Man's nature involves physical, vegetative, and animal levels of being. Thus, while man's knowledge of himself cannot replace empirical science, it abstracts a knowledge of these realms from his own being which, though limited, is not of the substitute sort, and thus transcends the limitations of his senses. So the argument goes; but it is, of course, confusion. Its plausibility rests on man's pre-scientific knowledge of himself, just as the pre- scientific knowledge of the physical world (the presence of which in sense-experience makes this so much more than seeing colors or hearing sounds) made plausible the abstractive theory of physical science. In each case, the fruit of the long process of pre- scientific learning is transmogrified into a bogus process of intuitive abstraction. The confusion is bolstered by the fact that such learning, like "intuitive abstraction" is not a matter of systematic and deliberate saving of appearances.


Let us now leave the subject of Neo-Thomist attempts to patch up the Aristotelian theory of knowledge, and return to an examination of the original theory, this time with a view to its bearing on the mind-body problem. We shall restrict our attention to the distinction, vital to the Aristotelian tradition, between the "active" and the "passive" reason.

Before we begin, let us remind ourselves that neither Aristotle nor the Scholastics conceived of soul and body as two changing, interacting substances, as did Plato and Descartes. The Aristotelians define the human soul as the substantial form of the human individual, who consists of matter and form as does any terrestrial substance. With qualifications which will be introduced at the proper place, it is the [559] human individual that acts, that does things, and not the soul; just as it is water that freezes, and not the nature of water.

Let us also remind ourselves that even should it be necessary (which it is not) to recognize the existence of unique acts of "intellection" which are not explainable in terms of psychological laws relating to linguistic activity, this would not by itself force us to adopt a dualism of mind and organism as separate or separable things. The recognition would lead us to expand our list of irreducible laws; and therefore to expand our list of irreducible dispositional properties. But just as we are not led to postulate a new thing every time we discover a new property of what we have been taking to be one thing, so the mere recognition of an irreducible set of acts and dispositions relating to thought would not call for a thing dualism of mind and body.26 It is only if we could show either that acts of thought are found to occur apart from the acts and dispositions characteristic of biological organisms, or else that they are completely independent of the remaining acts and dispositions of the organism, that we should be justified in arguing either that they belong to a separate thing, or, at least, that they will not be touched by the organism's death. The first alternative is that of finding empirical evidence for the existence of disembodied rational spirits. This, of course, can be left in the capable hands of the Psychical Research Society. It is a modified form of the second alternative which we find in Aristotle.

Let us now consider certain implications of the abstractive theory of thought, using as an example the proving of a geometrical theorem with the aid of a complex construction. We shall conceive of the process of proof as the successive grasping of ever more intricate relationships between the geometrical universals involved in the proof, a process culminating in the grasping of the proposition to be proved as necessitated by the relationships apprehended in the earlier stages of the proof.

We remember that, according to the abstractive theory, one cannot grasp a geometrical universal unless an instance of that universal is present to sense or imagination. Again, one cannot think of a triangle unless one is grasping the universal Triangularity. Now, suppose that at a certain stage in the argument the inscription of a circle is required by way of construction. It follows directly from the abstractive theory that one cannot think of constructing a circle in sense or imagination unless one is already aware of a sensed or imagined Circle. Thus, if we ask, "By what rational process is the geometrician led to make a new construction?" the answer must surely be, "None." The construction cannot be caused, even in part, by the thought of the [560] construction, for the thought of the construction presupposes the construction!

We can generalize this implication of the strict form of the abstractive theory. It is a necessary consequence of the theory that thought, abstracting the universals which define its subject matter from the data of the senses and imagination, must accept with natural piety what the senses and imagination offer it in the way of material for abstraction. The coming to have a kind of experience (sense or imagination) cannot have as its cause (in whole or in part) the thought of the kind of experience one comes to have.

We must hasten to qualify the conclusion of the preceding paragraph, for Aristotle, taking a hint from the Socratic Doctrine of Recollection, worked out a most ingenious theory to avoid this consequence of the abstractive theory. Before giving Aristotle's solution of this problem, let us reformulate the difficulty as accurately and completely as possible.

According to the abstractive theory of thought, the thought of X cannot be a causal factor in one's coming to experience a case of X, since in order to think of X one must already be experiencing a case of X. If this is the case, then sense and imagination yield material for coherent sequences of thought only per accidens. For example, imagination happens, owing to causes lying outside the intellect, to provide the series of imaginative constructions which make possible the grasping of ever more complicated relationships between geometrical universals which, according to the Aristotelian, is the process of arriving at a proof.

There would seem to be only two ways (within a generally Aristotelian framework) of avoiding this consequence.

The first -- relatively modern -- consists in distinguishing between "symbolic" or "substitute" thinking (which is characterized as a calculational activity of the imagination, a manipulating of symbols according to learned habits) and "real" thinking (which is a matter of grasping relationships between universals and other meanings). I took this approach myself in an earlier rationalistic stage of my philosophical development. Those who argue in this way insist that merely symbolic thinking rests on habits learned in connection with "real" thinking, which is abstractive in character. They seek to avoid the objection we have raised against the abstractive theory by claiming that a temporal process of thought is either a sequence of real thinking for which the orderly flow of abstractive material is [561] controlled by the rational or calculational habits of the imagination, or else is symbolic thinking through and through.

Concerning this first theory we limit ourselves to two arguments. (1) Those who take this course undercut, as we shall see, the ground on which rests the Aristotelian conception of the active intellect. (2) Once systematic and "rational" processes are recognized which are not apprehendings of universals or other types of meanings, then even though one insists that such apprehendings must exist as the necessary conditions of the existence of "symbolic" thinking, one is open to a line of refutation which argues that "symbolic" thinking can be empirically accounted for without postulating such apprehendings. I have made it clear that in my opinion such a line of refutation would be successful.

The other approach to our difficulty is that taken by Aristotle who, in common with almost all philosophers up to relatively recent times, overlooked the possibility of a psychology of linguistic activity which would interpret it as something other than a means of "expressing" and communicating "real" thinking. (Actually "real" thinking is a ghost of "linguistic" thinking which haunts the rationalist.)

Aristotle27 realized that unless thought somehow had a hand in the flow of imagination, the occurrence of the right image at the right time which is necessary (on the abstractive theory) for systematic temporal processes of thought, would be a mere matter of chance. Unwilling either to admit this or to abandon the abstractive theory, and overlooking the possibility of invoking "symbolic" thinking, he had to find some way of reconciling the abstractive theory of discursive thought with his conviction that thought as well as hunger, fear, etc., was a causal factor influencing the human imagination. Somehow we must be thinking of what we are going to think before we think it. This "prior" thinking (which, in the nature of the case cannot be the abstractive thinking it is designed to explain) is the active reason or intellectus agens (nous poietikos). The term "prior" is, of course, misleading, since the active intellect is, for Aristotle, a ceaseless activity of knowing all essences and what they involve. It does not change, since it does not first know one thing, then another, but always all things. The active reason is a "part" of the soul of each rational being who is capable of a science of the world; but whether there is one active reason for all, and how the active reason is related to the forms are questions which Aristotle never answered, or to which his answers have been lost. [562]

It is by the conception of the active intellect as a "part" of the human soul that Aristotle is enabled to hold that the flow of our experience is guided by thought -- guided in part, for clearly thought is not the sole cause of the course of experience; it competes with the appetitive nature of man. It is only by a complete misunderstanding of the requirements of the Aristotelian conception of thought that his active reason has so widely been interpreted as the act of abstracting the universal from the particular.28 The latter is an essential phase of temporal or passive reason which, "illuminated" by active reason, disengages the universal from the sensuous embodiment which the active reason, by influencing man's imagination in competition with other aspects of his nature, has made available to it. Discursive thought, for Aristotle, is the tenuous product of the impact on the imagination, which man shares with the brutes, of the unchanging and divine activity of pure thought which is the active reason. The latter is, of course, a thinking which is completely independent of sense, imagination, and temporal thought. It is therefore independent of the organism, and is not "touched" by death. It is the immortal "part" of the human soul.

As is well known, it is the impersonal immortality of the Aristotelian active reason which the Thomists have converted, under the pressure of Christian Dogma, and with the aid of the central confusions of the perennial philosophy, into the immortality of the human soul. Their argument can be tersely analyzed into the following steps:

(A) Each substance has only one substantial form. This is a direct consequence of the definition of a substantial form, since, properly understood, the substantial form of a substance is the unity of all the properties characteristic of that kind of substance. The error of maintaining that one substance can have a plurality of substantial forms comes from noting that higher level substances have properties of a kind which is also to be found in lower level substances -- the elephant can slide down the grassy slope -- while failing to note that these lower level properties of higher level substances take the form they do as bound up with the higher level properties of these substances. (See p. 546-7, above.) For the Scholastic it follows that it is a confusion to think of higher level substances as including lower level substances.29 It is said that the substantial forms of higher level substances include the substantial forms of lower level substances "virtually"30 by including their properties modified to fit their higher estate. [563]

(B) Thus, the substantial form of a rational animal is a unity which involves all the properties characteristic of human beings.

(C) But the substantial form of rational animals includes the intellectus agens or active reason.

(D) Now the intellectus agens is not just a property in virtue of which man does things. It is not, in our terminology, a dispositional property as is, say, vision. It does things. It knows;31 and knows in a way which is independent of the organism. Therefore the human soul is not just a unity of properties, it does something; it knows.

(E) Consequently, the human soul is not only the substantial form of the human individual, it is also a substance. For that which acts is a substance.

(F) Since the human soul is a unity which is in one aspect immortal, it is immortal as a whole. Therefore the entire human soul with all its dispositional properties, both original and acquired, is an immortal substance.

Now the crucial step in this argument is step C. Unfortunately it is a mistake. It by no means follows from the fact (granted that it is a fact) that human discursive thought could not occur without the influence of the active reason, that the latter is a part of the human soul, any more than it follows from the fact that without the sun the earth would not now move in an ellipse, that the sun is part of the earth. It is only because of the complete misunderstanding of the nature of a thing which we have traced in the course of our argument, that the active reason which (1) is not a dispositional property, and (2) is ex hypothesi completely independent of the organism, could be conceived of as "part" of the human substantial form. In general, it is only by pictorial thinking of the crudest sort that one can interpret the unity of a substantial form as other than a functional unity of dispositional properties. Indeed, it must not be just any functional involvement of dispositional properties (for, after all, the nature of gold includes the property of dissolving in aqua regia, and the nature of aqua regia includes that of dissolving gold) but only that sort of involvement which requires us to say that we are dealing with one thing rather than two. As the Averroists saw, what we have in the case of human reason (again, we are making the contrary-to-fact assumption that it makes sense to speak of an active reason at all) is two things, one of which, man, could not perform certain activities, i.e., think, unless the other, active reason, were influencing it (illumination).

Another argument from the nature of thought to such an [564] independence of thought from the body as might back up the dogma of the immortality of the soul can be dismissed even more briefly.

This time it is argued that the activities of "real" thought cannot be the acts of any organ (specifically, the brain), because universals are present in acts of organs only by way of actual exemplification, whereas in thought universals and other objects of intellect have being for thought or "intentional being." The argument continues (I quote from Mortimer Adler's What Man Has Made of Man, p. 179) as follows:

". . . (8) Therefore the intellect must receive universal forms. (9) But no form is universal according as it is received in matter. (10) Therefore intellectual reception must be immaterial, which is to say that understanding is not the act of a bodily organ. This last proposition is the capital premise for the conclusion that the soul, having this immaterial mode of operation, must also to that extent have an immaterial mode of being, and hence it is not only the substantial form of the body, but is capable of separate self-subsistence upon the corruption of the composite."

Now even granted that there is such a thing as the intellectual reception of universal forms -- in short, "real" thinking -- and that this notion is not merely the confused echo (due to the mixing of the psychological and the logical approaches to thought) of symbolizing habits and activities, even granted this, the argument is unsound. Everyone would surely admit that the fact that, if mechanism in biology be false, acts of organs are not acts of chemical elements, has not the slightest tendency to show that acts of organs are capable of separate existence apart from acts of chemical elements, in view of the dependence of acts of organs on acts of chemical elements. The situation is exactly the same with respect to the above argument. It must be granted that "intellectual receptions of universals" are not the acts of any bodily organ, for they are certainly of a different nature from those acts which we class as acts of organs. But intentional acts of the understanding (if such there be) are related at least as intimately to the biological activities of the nervous system as these biological activities are related to physicochemical activities. They are unique acts of the man who, by performing them, shows himself to be a substance of a higher level than the merely "organic" or biological.

The only difference between the case in point and proposed analogy lies in the pictorial dimension. Our imagery for physical and biological activities is robust and colorful; for "thought" it is pale [565] and bloodless. Thus we tend to think of intellectual activities as present only in a ghostly and tenuous way in the physical and biological turmoil; whereas the dependence of biological on the physical, though no greater, is depicted in terms of a pictorial involvement more adequate to the dependency. Once childish things are put aside (and pictorial thinking is childish) it is clear that from difference in kind to capacity for separate existence it is only possible to argue given lack of dependence. (The virtue of the argument from the active intellect was that there such independence was involved in the very argument which "established" the existence of the active intellect.) But given the degree of dependence of discursive thought on brain activity, with particular emphasis on symbolizing habits, which confronts the most casual study of scientific evidence, it is clear that the only acceptable argument for the possibility of the separate existence of thought must rest on evidence of the actual occurrence of separate thought. ("From actuality to possibility the argument is sound," to quote a Scholastic maxim.)

Thus, here again we are thrown back on the Psychical Research Society, unless an examination of the theological and ethical arguments for survival would prove more convincing. But that is beyond the scope of this essay.

Notes and References

* Wilfrid Sellars, M.A. (Oxford), is Associate Professor of Philosophy at the University of Minnesota, Rhodes Scholar at Oxford University, 1934-1937, taking First Class Honors in Philosophy, Politics, and Economics, 1936. Author of articles on epistemological topics in Philosophy and Phenomenological Research, the Journal of Philosophy, and Philosophy of Science. Co-editor with Herbert Feigl of Readings in Philosophical Analysis.

1 The phrase "formal materialism" frequently occurs in contemporary Thomist literature as an alternative to "hylomorphism," particularly when it is a question of wooing intellectuals whose quest for certainty has led them to flirt with "dialectical" materialism, or any other philosophy avowedly materialistic in character, and for whom this phrase might build a bridge to the eternal verities. See Mortimer Adler, What Man Has Made of Man (1938), pp. 167 ff. 180. For an elementary statement of Thomistic hylomorphism, see Maritain, Introduction to Philosophy (1930), pp. 166 ff.

2 I wish to acknowledge my indebtedness to Prof. C.D. Broad's discussion of dispositional properties and the concept of the nature of a thing in An Examination of McTaggart's Philosophy (1933), Vol I. pp. 142-151, 264-278. See also chap. X of his The Mind and Its Place in Nature.

3 Note that the contrast between "state" and "circumstance" belongs to the thing-nature language. Causal laws conceived of as functional correlations of events are not formulated in terms of "states" and "circumstances." The relation the thing-nature or thing-property language to the event-law language is not the simple one of whole to part. Laws are formulated differently in these two frameworks. See also note 5 below.

4 It is especially significant to the historian of philosophy that the thing-nature framework, though historically prior to and more "natural" than the event-law framework which was to dominate science from the seventeenth century on, could be correctly analyzed only by a philosopher who has a clear conception of a law of nature, and that although many if not all laws can be formulated in both the event-law and the thing-nature framework, attention is explicitly focused on laws only in the process of research which must make use of event-law framework. The language of things and properties, states and circumstances, where it is appropriate, sums up what we know. But the scientist doesn't know what kinds of things there are until he has arrived at laws which can be translated into the thing language. Thus, the historian infers that one would hardly expect to find a correct analysis of the thing-nature framework until scientists were explicitly looking for causal laws. He also infers that, unless the thing-nature framework is essential to science, it would be discarded by the scientist in favor of the event-law framework, so that the motivation for such an analysis would be lacking at the very time it became possible. The history of philosophy bears out both these inferences. On the other hand, the historian would expect that, should it ever become either necessary or convenient to formulate certain areas of knowledge in the language of things and dispositions, philosophers of science would soon reexamine this framework.

5 Whether the elaboration of concepts within the thing-nature framework is anything more than a convenient common- sense dodge, whether it is, in the last analysis, self-consistent, and, indeed, whether this elaboration is possible with anything other than the crudest laws, are questions into which we shall not enter. For a discussion of these and other questions which together make up the philosophical problem of "substance," the reader is referred to Prof. Everett J. Nelson's essay in this volume.

6 Adler, op. cit., pp. 111, 190.

7 Leibniz was to realize that the necessity with which the states of things occur, given their natures and circumstances, is analytic or tautological, but, owing to a confusion about relations, was to think that a reference to circumstances could not be involved in the definition of the nature of a substance. More accurately, this confusion led him to conceive of the circumstances to which a substance responds by taking on a given state as other states of the same thing. For this to be plausible, he had to put environment of each thing inside the thing. The result was his famous doctrine that each monad or substance mirrors the entire universe.

8 "Essence and power are distinct, but the powers flow from essence." -- Adler, Problems for Thomists: The Problem of Species, p. 182.

9 Aristotle thought that historically the higher could not come from the lower, and believed that all natural kinds have existed from eternity, because he confused "coming from" with "reducible to." Contemporary Aristotelians who are aware of the distinction rightly see no incompatibility between "irreducible levels" and "evolution."

10 A.E. Taylor, in his Varia Socratica, has shown that by the time of Socrates the term "idea" (eidos, idea), which originally referred to the human form, had become a technical term for the ultimate ingredients which mix and unmix to form the world process. Thus Democritus referred to his atoms as Ideas. Compare the process by which the German word Gestalt has become a technical term in psychology, and, indeed, in philosophy.

11 The solution of the problem of universals consists exactly in showing that the following statements are all true: (1) "Universals exist." (2) "Thoughts mean universals." (3) "It is nonsense to speak of any psychological relationship between thought and universals." The solution involves first a making explicit of the ambiguities of the term "existence," and second a distinction between "meaning" as a term belonging to the framework of logical analysis and criticism, and "meaning" as a descriptive term in empirical psychology relating to habits of response to and manipulation of linguistic symbols. The classical conception of mind as apprehending universals and meaning is based on a confusion of the logical with the psychological frame of reference. To deny that universals "exist" when speaking in the framework of logical analysis (logical nominalism) is as mistaken as to assert that universals "exist" when speaking in the framework of the psychological description of thought (ontological realism or Platonism).

12 Recent logical analysis has made it clear that just as every thought involves a reference to at least one universal, so every thought -- even the most "abstract" - - involves a reference to at least one particular. Indeed, instead of abstract thoughts referring to no particulars, the exact opposite is the case, for they refer to all particulars. Thus, "All A is B" says of every item in the universe that if it is an A it is also a B. This line of thought cannot be explored on this occasion. It is sufficient to note that, if sound, it explodes the Platonic contention that universals are more appropriately the objects of thought than are particulars.

13 It is often said that the essential difference between Platonist and Aristotelian is that while both maintain the ontological reality of universals, the Aristotelian holds that they exist only in particulars, the Platonist giving them an existence apart. One should always be cautious about attributing nonsense to intelligent philosophers; and to say that universals are literally in (or apart from) particulars is nonsense. This interpretation of the difference between Platonist and Aristotelian rests on two mistakes. (1) It overlooks the fact that the "apartness" of the Platonic Ideas is, in large measure, their Olympian self-sufficiency. Plato teaching -- except in the Parmenides -- that the Ideas would exist even if the "world of becoming" did not. (2) It rests on the assumption that the Aristotelian clearly and unambiguously thinks of his forms as "objective" universals, for that the forms of changing things exist only as ingredients of these things for this philosophy is granted. The truth of the matter is that the Aristotelian has a strong bias against the ontological reality of universals, and tends to think of them as contents "abstracted" from sense and imagination, which contents become universals only in and for thought. The Aristotelian matter can scarcely be a principle of particularity which supplements universals (as it is for the Platonist); otherwise "pure forms" would be universals, which they clearly are not intended to be. Matter makes change possible, and in doing so is a principle of difference for objects having like nature; for objects of like nature can differ only in their histories. Matter is the principium individuationis rather than principium particularitatis. It must be admitted, however, that the Aristotelian has his Platonizing moments, especially when puzzled about the objectivity of knowledge. Notice that I have been speaking of the Aristotelian tradition rather than of Aristotle himself. A discussion of the extent to which the latter exhibits the characteristic ambivalence of the Aristotelian tradition with respect to the status of universals would take us far beyond the scope of this paper. Fortunately, the argument which follows does not depend on either interpretation of the Aristotelian theory of universals. For a penetrating account of Aristotle's difficulties with universals see H.F. Cherniss, Aristotle's Criticism of Plato and the Academy, Vol. I (1944), pp. 324-376. For the Thomist treatment of the problem see Maritain, Introduction to Philosophy, pp. 160 ff.; Mortimer Adler, "Solution of the Problem of Species," Thomist, Apr., 1941, pp. 303 ff. See also Maritain, La Philosophie de la nature, p. 9.

14 De Anima, Bk. III, chaps. 7, 8. See W.D. Ross, Aristotle, 2nd ed., p. 148; Mortimer Adler, What Man Has Made of Man, pp. 162, 175; Maritain, Introduction to Philosophy, pp. 170 ff.; R.E. Brennan, Thomistic Psychology (1942), p. 179 ff., 202. Cf. Brennan's discussion of imageless thought on p. 204, where in his eagerness to reconcile Aquinas with empirical fact, he contradicts not only the entire Aristotelian tradition, but what he has himself just finished saying.

15 Republic, VI, pp. 510-511.

16 The Doctrine of Recollection (Phaedo, pp. 72-77; Meno, pp. 80-86) might be thought, at a hasty glance, to be or entail such a position. Plato's point, however, is that the object of thought can neither be nor be derived from the object of the senses. He also assumes that the objects of thought cannot be directly grasped by an embodied soul (an assumption which Plato himself later abandoned, and with it the Doctrine of Recollection which falls without it). When the object of sense seems to be the object of thought it is because it is putting us in mind of the object of thought of which we must have an innate non-sensuous image or imprint). He argues that what reminds us of an idea need not be like the Idea. While he puts this forward in the Phaedo to reconcile recollection with the great difference between sense-objects and Ideas, it is clear that Plato does not intend to restrict the stimulus of recollection to sense- experience alone. Interrogation also can put us in mind of Ideas.

17 Ross, Aristotle, 2nd ed., pp. 136-142; Brennan, Thomistic Psychology, pp. 11-16, 117-123; Maritain, The Degrees of Knowledge (1938), p. 143 n.

18 Note that the science of the geometrical properties of color patches will not be the same as the science of the geometrical of physical objects, unless the terms "triangular," "straight," "shape," etc., have the same sense in the context of physical objects as they do in the context of color patches. Now the important thing about the shapes of color patches is that they are directly given to consciousness, so that, if there is a mental activity of abstraction as conceived of by the Aristotelians, it will make sense to speak of grasping geometrical universals by abstraction from cases with which the mind is directly acquainted. furthermore, if the geometrical universals exemplified by physical objects can reasonably be identified with the geometrical universals exemplified by the boundaries of colors, then the science in question would be the science of the shapes, of physical objects as well as of the shapes of color patches. If we assume, in Aristotelian style, that the colors we see are in the observer's organism, then the science of physical shapes would rest on the exemplification in the knower's organism of geometrical universals. Compare the case of the science of lions in the next paragraph.

19 See, for example, Thomistic Psychology, pp. 178, 184, 189-193.

20 "We must . . . notice that dispositions fall into a hierarchy. A bit of iron which has been put inside a helix in which an electric current circulates acquires the power to attract iron-filings. . . . If we call this magnetic property a 'first-order disposition,' the power to acquire this property when placed in a helix . . . may be called a 'second-order disposition.' " (Broad, Examination of McTaggart's Philosophy, Vol. 1, p. 266.) See also the references listed in note 2 above.

21 Maritain, La Philosophie de la nature, pp. 42, 89-93; Maritain, The Degrees of Knowledge, p. 249; Brennan, op. cit., p. 170; Adler, "Solution of the Problem of Species," pp. 399 n., 347 n. Adler has apparently not got around to drawing the implications of his remarks in the latter reference. They contain enough dynamite to force a complete revision of his ontology, or epistemology. Is substantial form a category in the Kantian sense?

22 Adler, What Man Has Made of Man, p. 207; Maritain, The Degrees of Knowledge, pp. 77, 168, 216, and La Philosophie de la nature, pp. 100, 143.

23 Maritain, La Philosophie de la nature, pp. 75-80, and The Degrees of Knowledge, p. 249, also pp. 77, 168, 216.

24 Maritain, La Philosophie de la nature, pp. 75, 110, 140-143, and The Degrees of Knowledge, pp. 168, 216-217.

25 Mortimer Adler, What Man Has Made of Man, p. 187. On the value of pre-scientific experience for philosophy, see Adler's distinction between general and special experience, op. cit., pp. 11, 57, 129, 131; see also Maritain, La Philosophie de la nature, pp. 89-93. On the ability of the philosophy of nature to penetrate "behind" phenomena, see also Adler, op. cit., pp. 28, 160. But cf. the reference commented on in note 21 above.

26 The traditional mind-body problem is unnecessarily confused by a careless use of the term "interaction." Properly, this term belongs in the thing-language, and denotes a relation between things or substances. However, it is sometimes used by philosophers in such a way that it means only a causal entanglement of two series of events of fundamentally different kinds. The latter use analytically presupposes "qualitative" dualism, and if mental events are "irreducible" there is interaction in this sense. Usually at this stage the ordinary sense of interaction takes over and, presto chango, our philosopher has a dualism of interacting mental and physical things. Whether or not the thing-language is anything more than a common-sense dodge, it is important to note that qualitative dualism of events does not, by itself, entail dualism of things. This insight is characteristic of the Aristotelian tradition, as of modern emergentist theories.

27 De Anima, Bk. III, chap. 5; see also 413a 3-7, 413b24-29 and 429b3-4. The basis in what survives of Aristotle's works for a reconstruction of his distinction between active and passive reason is extremely tenuous, amounting to but a few sentences of explicit discussion. The interpretation which I offer is, I believe, not only compatible with what he does say, and with the analogies from other areas stressed by commentaries, but is a reasonable argument, given his premises. For an account of the evidence as well as of the main lines of interpretation see Ross, Aristotle, 2 nd ed., pp. 148-153, and E. E. Spicer, Aristotle's Conception of the Soul (1934), pp. 103-112.

28 "Abstraction, which is the proper task of the active intellect . . . " (Brennan, Thomistic Psychology, p. 191.) See Ross's comment on this type of mistake on p. 149 of his Aristotle.

29 Except potentially. If you kill an elephant, earth, air, fire, and water, which were present in the living elephant only as physical properties, come into existence as substances. I shall not comment on this theory as it would take us too far into the analysis of substantiality, and would be irrelevant to the specific confusions involved in the argument for immortality, See Maritain, The Degrees of Knowledge, p. 219n.

30 See Adler What Man Has Made of Man, p. 190.

31 In so far as the Scholastics attributed to active reason the function of abstracting the universal from its sensuous embodiment, a dispositional property is involved which is essentially bound up with organic existence. This property and hence the act of abstraction, is therefore more properly attributed to the men than to the intellectus agens. The latter should be restricted to the timeless knowing of all natures.

Transcribed into hypertext by Andrew and Kathy Chrucky, May 10, 1997; revised Oct. 20, 1997: original page numbers have been inserted in brackets.