Writers seem to be divided into three camps on this question of other minds.

(1) I have treated our knowledge of other minds as due to an inference.  This is the position usually taken.

(2) We have seen that Huxley and Clifford cast doubts upon the validity of the inference, but, nevertheless, made it.  Professor Strong, in the work mentioned in the notes to the previous chapter, maintains that it is not an inference, and that we do not directly perceive other minds, but that we are assured of their existence just the same.  He makes our knowledge an “intuition” in the old-fashioned sense of the word, a something to be accepted but not to be accounted for.

(3) Writers who have been influenced more or less by the Neo-Kantian or Neo-Hegelian doctrine are apt to speak as though we had the same direct evidence of the existence of other minds that we have of the existence of our own.  I have never seen a systematic and detailed exposition of this doctrine.  It appears rather in the form of hints dropped in passing.  A number of such are to be found in Taylor’s “Elements of Metaphysics.”

Section 43.  The “Mind-stuff” doctrine is examined at length and its origin discussed in Chapter XXXI of the “System of Metaphysics,” “Mental Phenomena and the Causal Nexus.”  It is well worth while for the student to read the whole of Clifford’s essay “On the Nature of Things-in-themselves,” even if he is pressed for time.

CHAPTER XI, section 44.  See “System of Metaphysics,” Chapter XV, “The World as Mechanism.”

Section 45.  See Chapter XXXI, “The Place of Mind in Nature.”

Section 46.  For a definition of Fatalism, and a description of its difference from the scientific doctrine of Determinism, see Chapter XXXIII, “Fatalism, ‘Freewill’ and Determinism.”  For a vigorous defense of “Freewill” (which is not, in my opinion, free will at all, in the common acceptation of the word) see Professor James’s Essay on “The Dilemma of the Determinist,” in his volume, “The Will to Believe.”

Fatalism and Determinism are constantly confused, and much of the opposition to Determinism is attributable to this confusion.

Section 47.  See Chapter XXXII, “Mechanism and Teleology.”

CHAPTER XII, section 48.  The notes to Chapter III (see above) are in point here.  It is well worth the student’s while to read the whole of Chapter XI, Book IV, of Locke’s “Essay.”  It is entitled “Of our Knowledge of the Existence of Other Things.”  Notice the headings of some of his sections:—­

Section 1.  “It is to be had only by sensation.”

Section 2.  “Instance whiteness of this paper.”

Section 3.  “This, though not so certain as demonstration, yet may be called ‘Knowledge,’ and proves the existence of things without us.”

Locke’s argument proceeds, as we have seen, on the assumption that we perceive external things directly,—­an assumption into which he slips unawares,—­and yet he cannot allow that we really do perceive directly what is external.  This makes him uncomfortably conscious that he has not absolute proof, after all.  The section that closes the discussion is entitled:  “Folly to expect demonstration in everything.”