For this the associationist must introduce the order of experience in the outer world.The dance of the ideas is a copy, somewhat mutilated and altered, of the order of phenomena.But the slightest reflection shows that phenomena have absolutely no power to influence our ideas until they have first impressed our senses and our brain.The bare existence of a past fact is no ground for our remembering it.Unless we have seen it, or somehow undergone it , we shall never know of its having been.The experiences of the body are thus one of the conditions of the faculty of memory being what it is.And a very small amount of reflection on facts shows that one part of the body, namely, the brain, is the part whose experiences are directly concerned.If the nervous communication be cut off between the brain and other parts, the experiences of those other parts are non-existent for the mind.The eye is blind, the ear deaf, the hand insensible and motionless.And conversely, if the brain be injured, consciousness is abolished or altered, even although every other organ in the body be ready to play its normal part.A blow on the head, a sudden subtraction of blood, the pressure of an apoplectic hemorrhage, may have the first effect; whilst a very few ounces of alcohol or grains of opium or hasheesh, or a whiff of chloroform or nitrous oxide gas, are sure to have the second.The delirium of fever, the altered self of insanity, are all due to foreign matters circulating through the brain, or to pathological changes in that organ's substance.The fact that the brain is the one immediate bodily condition of the mental operations is indeed so universally admitted nowadays that I need spend no more time in illustrating it, but will simply postulate it and pass on.The whole remainder of the book will be more or less of a proof that the postulate was correct.
Bodily experiences, therefore, and more particularly brain-experiences, must take a place amongst those conditions of the mental life of which Psychology need take account.The spiritualist and the associationist must both be 'cerebralists,' to the extent at least of admitting that certain peculiarities in the way of working of their own favorite principles are explicable only by the fact that the brain laws are a codeterminant of the result.
Our first conclusion, then, is that a certain amount of brain-physiology must be presupposed or included in Psychology.
In still another way the psychologist is forced to be something of a nerve-physiologist.Mental phenomena are not only conditioned a parte ante by bodily processes; but they lead to them a parte post.That they lead to acts is of course the most familiar of truths, but I do not merely mean acts in the sense of voluntary and deliberate muscular performances.Mental states occasion also changes in the calibre of blood-vessels, or alteration in the heartbeats, or processes more subtle still, in glands and viscera.If these are taken into account, as well as acts which follow at some remote period because the mental state was once there, it will be safe to lay down the general law that no mental modification ever occurs which is not accompanied or followed by a bodily change.The ideas and feelings, e.g., which these present printed characters excite in the reader's mind not only occasion movements of his eyes and nascent movements of articulation in him, but will some day make him speak, or take sides in a discussion, or give advice, or choose a book to read, differently from what would have been the case had they never impressed his retina.Our psychology must therefore take account not only of the conditions antecedent to mental states, but of their resultant consequences as well.
But actions originally prompted by conscious intelligence may grow so automatic by dint of habit as to be apparently unconsciously performed.Standing, walking, buttoning and unbuttoning, piano-playing, talking, even saying one's prayers, may be done when the mind is absorbed in other things.The performances of animal instinct seem semi-automatic, and the reflex acts of self-preservation certainly are so.Yet they resemble intelligent acts in bringing about the same ends at which the animals' consciousness, on other occasions, deliberately aims. Shall the study of such machine-like yet purposive acts as these be included in Psychology?
The boundary-line of the mental is certainly vague.It is better not to be pedantic, but to let the science be as vague as its subject, and include such phenomena as these if by so doing we can throw any light on the main business in hand.It will ere long be seen, I trust, that we can; and that we gain much more by a broad than by a narrow conception of our subject.At a certain stage in the development of every science a degree of vagueness is what best consists with fertility.
On the whole, few recent formulas have done more real service of a rough sort in psychology than the Spencerian one that the essence of mental life and of bodily life are one, namely, 'the adjustment of inner to outer relations.' Such a formula is vagueness incarnate; but because it takes into account the fact that minds inhabit environments which act on them and on which they in turn react; because, in short, it takes mind in the midst of all its concrete relations, it is immensely more fertile than the old-fashioned 'rational psychology,' which treated the soul as a detached existent, sufficient unto itself, and assumed to consider only its nature and properties.I shall therefore feel free to make any sallies into zoology or into pure nerve-physiology which may seem instructive for our purposes, but otherwise shall leave those sciences to the physiologists.
Can we state more distinctly still the manner in which the mental life seems to intervene between impressions made from without upon the body, and reactions of the body upon the outer world again? Let us look at a few facts.
