2 This distinction originates from Charles Peirce; cf. his Collected Papers, Harvard University Press, Cambridge, 1934, Vol. V, p. 50 (originally published 1903). Historically the introduction of symbols may be reducible to iconic signs; thus the hieroglyphics were originally pictures of objects. Furthermore, the onomatopoetic words, occurring in all languages, are iconic signs.

3 The distinction between tokens and the class of tokens applies also to nonlinguistic signs.

4 We do not distinguish between 'proposition', 'sentence', and 'statement', and shall therefore use these terms interchangeably.

5 The two first letters 'al' of the Turkish word constitute the verb root meaning 'to buy'; the three letters 'bill' represent the root of a verb meaning 'to be able'. The rest consists of suffixes.

6 For a presentation of these ideas and a general exposition of the verifiability theory of meaning, cf. the author's Experience and Prediction, University of Chicago Press, Chicago, 1938, chapter I. We refer toTthis book also for an analysis of the meaning of 'truth'.