for definite functions. I think that anatomy and physiology bear me out. And as for consciousness being intense only when 'nerve processes are hesitant': what of the plunge into cool water on a hot day? what of the enjoyment of music after a long æsthetic starvation? what of our grief at the loss of a dear friend?
The second argument I take to be misleading. Vicarious function has its limits. We can never see by aid of the auditory center, or hear by aid of the visual. But the brain is bilaterally symmetrical; its centers are arranged in a hierarchy, one above another; the connections of center with center, direct and indirect, are multitudinous. Vicarious function is thus, within wide limits, possible and natural; the excitation whose 'principal path' is blocked finds several 'secondary paths' still open. Let all the paths for a given form of excitation be blocked, however, and what happens? Here is the supreme occasion when consciousness might be useful; and consciousness does nothing.
The third argument requires a somewhat more detailed examination. It is an empirical law, a rule of average, that pleasant things are good for the organism, and unpleasant things bad. Pleasant things, things that we like, are things which, presented as stimuli, evoke movements of extension or approach; unpleasant things, things which we do not like, repel us,—we shrink from them. The usual explanation of the law is that organisms which (as psychical) liked and (as physical) reached out after things that were bad for them would, in the long run, be killed off. It is a condition of living that the things sought after shall, on the whole, be good for the seeker. The argument alleges that this explanation is insufficient. 'If pleasures and pains' as such 'have no efficacy,' there is no reason why their relation should not be reversed; why the things that are bad for us should not be pleasant, and the good things unpleasant.
I think that the argument, by its very formulation, assumes the causal efficacy which it is meant to prove. It assumes that a change of mental process must necessarily condition a corresponding change of motor reaction. Now there is good biological reason—psychology apart—why the things that are bad for us should not be sought after, and the things that are good for us neglected or repelled. But what mental process colors the 'sought after' and the 'repelled' is simply a question of fact. If it is the peculiar quality of pleasure and pain that we are asked to account for, I reply that we can no more explain this than we can explain why ether waves of a certain frequency correspond to the sensation quality 'red' and not to that of 'blue.' If it is the constancy of the mental accompaniment that is at issue—and this is suggested by the reference to an 'a priori rational harmony'—I reply that the constancy is a given fact, accepted by parallelist and interactionist alike, just as it is in the case of the colors. The argument, so far as I