The conclusion we have reached in this chapter is that William James was right in his views on “consciousness”. No mental occurrence has, in its own intrinsic nature, that sort of relational character that was implied in the opposition of subject and object, or of knower and known. Nevertheless we can distinguish “mental” events from others, and our most indubitable knowledge is concerned with a certain class of mental events. We have arrived at this result by following out to its logical conclusion the behaviourist definition of knowledge which we gave in Chapter VIII. We have had to modify considerably the point of view which originally led us to that definition, the modification having been forced upon us by the physical knowledge which, starting from a common-sense realism, has been gradually driven, through the causal theory of perception, to a view of cognition far more subjective than that from which physicists, like the rest of mankind, originally set out. But I do not see how there can be any escape from this development. CHAPTER XXI EMOTION, DESIRE, AND WILL Hitherto, in our investigation of man from within, we have considered only the cognitive aspect, which is, in fact, the most important to philosophy. But now we must turn our attention to the other sides of human nature. If we treat them more briefly than the cognitive side, it is not because they are less important, but because their main importance is practical and our task is theoretical. Let us begin with the emotions.