And until one has attained to such a conception, the statement that the mind is immaterial must remain rather vague and indefinite.  As we saw above, even the Plotinic soul was inconsistently material rather than immaterial.  It was not excluded from space; it was referred to space in an absurd way.  The mind as common sense conceives it, is the successor of this Plotinic soul, and seems to keep a flavor of what is material after all.  This will come out in the next chapter, where we shall discuss mind and body.

33.  THE PSYCHOLOGIST AND THE MIND.—­When we ask how the psychologist conceives of the mind, we must not forget that psychologists are many and that they differ more or less from each other in their opinions.  When we say “the psychologist” believes this or that, we mean usually no more than that the opinion referred to is prevalent among men of that class, or that it is the opinion of those whom we regard as its more enlightened members.

Taking the words in this somewhat loose sense, I shall ask what the psychologist’s opinion is touching the four points set forth in the preceding section.  How far does he agree with the plain man?

(1) There can be no doubt that he refers the mind to the body in some way, although he may shake his head over the use of the word “in.”

(2) As to whether the mind acts and reacts with matter, in any sense of the words analogous to that in which they are commonly used, there is a division in the camp.  Some affirm such interaction; some deny it.  The matter will be discussed in the next chapter.

(3) The psychologist—­the more modern one—­inclines to repudiate any substance or substratum of the sort accepted in the Middle Ages and believed in by many men now.  To him the mind is the whole complex of mental phenomena in their interrelations.  In other words, the mind is not an unknown and indescribable something that is merely inferred; it is something revealed in consciousness and open to observation.

(4) The psychologist is certainly not inclined to regard the mind or any idea belonging to it as material or as extended.  But he does recognize implicitly, if not explicitly, that ideas are composite.  To him, as to the plain man, the image held in the memory or imagination seems to be extended, and he can distinguish its parts.  He does not do much towards clearing away the difficulty alluded to at the close of the last section.  It remains for the metaphysician to do what he can with it, and to him we must turn if we wish light upon this obscure subject.

34.  THE METAPHYSICIAN AND THE MIND.—­I have reserved for the next chapter the first two points mentioned as belonging to the plain man’s doctrine of the mind.  In what sense the mind may be said to be in the body, and how it may be conceived to be related to the body, are topics that deserve to be treated by themselves in a chapter on “Mind and Body.”  Here I shall consider what the metaphysician has to say about the mind as substance, and about the mind as nonextended and immaterial.