37.  THE DOCTRINE OF THE PARALLELIST.—­Thus, the parallelist is a man who is so impressed by the gulf between physical facts and mental facts that he refuses to regard them as parts of the one order of causes and effects.  You cannot, he claims, make a single chain out of links so diverse.

Some part of a human body receives a blow; a message is carried along a sensory nerve and reaches the brain; from the brain a message is sent out along a motor nerve to a group of muscles; the muscles contract, and a limb is set in motion.  The immediate effects of the blow, the ingoing message, the changes in the brain, the outgoing message, the contraction of the muscles—­all these are physical facts.  One and all may be described as motions in matter.

But the man who received the blow becomes conscious that he was struck, and both interactionist and parallelist regard him as becoming conscious of it when the incoming message reaches some part of the brain.  What shall be done with this consciousness?  The interactionist insists that it must be regarded as a link in the physical chain of causes and effects—­he breaks the chain to insert it.  The parallelist maintains that it is inconceivable that such an insertion should be made.  He regards the physical series as complete in itself, and he places the consciousness, as it were, on a parallel line.

It must not be supposed that he takes this figure literally.  It is his effort to avoid materializing the mind that forces him to hold the position which he does.  To put the mind in the brain is to make of it a material thing; to make it parallel to the brain, in the literal sense of the word, would be just as bad.  All that we may understand him to mean is that mental phenomena and physical, although they are related, cannot be built into the one series of causes and effects.  He is apt to speak of them as concomitant.

We must not forget that neither parallelist nor interactionist ever dreams of repudiating our common experiences of the relations of mental phenomena and physical.  Neither one will, if he is a man of sense, abandon the usual ways of describing such experiences.  Whatever his theory, he will still say:  I am suffering because I struck my hand against that table; I sat down because I chose to do so.  His doctrine is not supposed to deny the truth contained in such statements; it is supposed only to give a fuller understanding of it.  Hence, we cannot condemn either doctrine simply by an uncritical appeal to such statements and to the experiences they represent.  We must look much deeper.

Now, what can the parallelist mean by referring sensations and ideas to the brain and yet denying that they are in the brain?  What is this reference?

Let us come back to the experiences of the physical and the mental as they present themselves to the plain man.  They have been discussed at length in Chapter IV.  It was there pointed out that every one distinguishes without difficulty between sensations and things, and that every one recognizes explicitly or implicitly that a sensation is an experience referred in a certain way to the body.