Roderick Firth, Sense Data and the Percept Theory, 1949-50.

4. THE PERCEPT THEORY AND EPISTEMOLOGICAL MONISM

Epistemological monists from Berkeley to many contemporary realists have used the theory that sense-data are epistemologically basic as a premiss in their attacks on epistemological dualism. Knowledge of physical objects is possible, they have said, only if statements about physical objects can be construed, in some more or less complex manner, as statements about sense-data -- or only, as some of them have preferred to say, if physical objects are somehow "composed of" sense-data. Their analysis of physical statements has not usually been based entirely on epistemological considerations, but in most cases their analysis was at least suggested by these considerations.

If the Percept Theory is true, however, the epistemological advantages traditionally attributed to monism can be retained only by reinterpreting statements about the physical world in terms of ostensible physical objects and events instead of sense-data. For one effect of the Percept Theory, as we have seen, is to change the denotation of the term "epistemologically basic". In whatever sense, therefore, a philosopher wishes to maintain that physical objects are "composed of" things that are epistemologically basic, in that sense he must say, if he accepts the Percept Theory, that physical objects are "composed of" ostensible physical objects. I do not propose to evaluate the results of such a reinterpretation but only to indicate what form it must take, and in particular to point out that ostensible physical objects can vary in ways that sense-data cannot, so that a new problem is uncovered as soon as we attempt such a reinterpretation.

To state this problem clearly let us say that according to the traditional forms of epistemological monism every physical object is a "family" of sense-data.70 If we do not specify the ontological status of sense-data -- whether, for example, they can exist unsensed and whether they may be "hypothetical" -- this statement can be interpreted as expressing a point of agreement among epistemological monists whether they be called "idealists", "realists", or "phenomenalists". For a family of sense-data would simply be the class of all those sense-data, actual or possible, which would have to be mentioned in making a complete ontological analysis of a particular physical object.

Now according to the traditional Sense-datum Theory, as we have seen, the sense-data observable by any one sense are quite limited in their qualities; visual sense-data, for example, may vary only in shape and colour. If the shape and colour of a visual sense-datum remain unaltered throughout a given period of time, therefore, changes in the attitude of the observer during that period cannot be said to affect the sense-datum at all. In the case of ostensible physical objects, however, the case is quite different; the colour and shape of two ostensible tomatoes may be exactly similar although the ostensible tomatoes, because of changes in the attitude of the observer, are quite different in other respects. To a hungry man the tomato may be presented as warm and sweet and edible whereas to someone looking for a missile it may be presented as soft and juicy and just about as heavy as a baseball. Thus it is clear that a family of ostensible physical objects is even more numerous than a family of sense-data, and that the relations among its members are many times more complicated. As a matter of fact it might even be more appropriate to say that a physical object is nothing less than a nation of sense-data, the nation in its turn comprising as many famines as there are attitudes capable of affecting the content of perceptual experience. Thus the various perspective views of a tomato which are obtained by walking around it, could be said to be members of one family provided that they are all determined by the same attitude. And by walking around the tomato a second time, but with a different attitude, the ob server could be said to become acquainted with members of a second family. And so on.

A philosopher who wished to maintain such a position, however, might not feel obliged to hold that members of all these families must be mentioned in an ideal translation of every statement about the tomato in question. He might insist, and with considerable plausibility, that what the hungry man means when he uses the word "tomato" is likely to be quite different from what the man in search of a missile means when he uses the same word, and that this difference in meaning must he reflected, in an adequate analysis, by the choice of families to be represented in the translation. Thus there might often be cases in which the meaning of the statement "This is a tomato", if used to express the limited belief of a particular observer, might be adequately translated into statements about ostensible physical objects which belong to very few families within the nation, or perhaps to only one. This is not the place to examine such possibilities more fully; it is sufficient for present purposes to point out that the Percept Theory creates a new problem for the epistemological monist, but that this new problem does not appear insoluble.

5. CONCLUSION

We may finally conclude, therefore, that there are at least four important epistemological implications of the Percept Theory:
  1. The traditional psychological distinction between the given and its meaning or interpretation, must usually be construed as a distinction between the ostensible physical object and certain accompanying events, either phenomenal or physiological or both.
  2. There is one traditional meaning of "the given", however, for which there is no simple substitute in terms of the Percept Theory; for this particular meaning a more complex substitute may be provided by means of a "definition in use".
  3. The denotation of the term "epistemic" must be understood to be ostensible physical obiects rather than those things which have traditionally been called "sense data".
  4. As a result of this fact all the traditional forms of epistemological monism must be reinterpreted to make physical objects "nations" of ostensible physical objects rather than than "families" of sense-data.

On the other hand the Percept Theory has no implications concerning the general epistemological or ontological status of physical objects. It does not imply that some form of epistemological monism must be correct, nor even that there is some reasonable sense in which it would be true to say, in an epistemological context, that physical objects are "directly presented" in perception. Those philosophers are mistaken, therefore, who have inferred from the Percept Theory that the traditional problems concerning the epistemology of perception are pseudo-problems, or that they must be completely recast to make them fit the phenomenological facts on which the Percept Theory is based.

The epistemological implications of the Percept Theory, we may conclude, are important but not revolutionary.

AUTHOR'S NOTE

Since this essay was written, the doctrine has become widespread among philosophers that it is a mistake (or, at the very least, misleading) to employ any form of "act-object" terminology to describe sense experience -- any terminology, that is to say, in which sense experience is represented as an act of perceiving, sensing, experiencing, having, or being aware of such "objects" as appearances, images, sensa, or sense-data; and with respect to this doctrine it is of course just as wrong to say that in perception we are aware of percepts or ostensible objects as to say that we are aware of sense-data. It is important to recog nize, therefore, that the phenomenological and epistemological issues discussed in this essay are entirely independent of the act-object terminology. They can be formulated in any terminology which allows us to describe a sensory constituent which may occur in hallucination as well as in "genuine" perception. If we agree, for example, to use the idiom "It looks as if I am seeing ----" for this purpose, the phenomenological issues discussed in Part I, Section 3 of this essay can be construed as issues concerning the types of words which may properly be inserted in the blank. It may be true, when I gaze at a snow-capped mountain, that it looks as if I am seeing a triangular patch of white. Can it also be true in this same purely sensory use of "looks as if" that it looks as if I am seeing a mountain capped with snow? Or, as so many philosophers have traditionally maintained, are we confusing the phenomenology of sense experience with an "interpretation" when we use words like "mountain" and "snow", and thus failing to describe our sense experience as it is really given? All the phenomenological and epistemological issues discussed in this essay may be formulated in some analogous way, using whatever idiom is approved by those who want to avoid an act-object terminology.

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Notes

70 The term, of course, is the one used by Price for a collection of sense-data unified in a certain way. See Perception, p. 227.

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