Sentence:  Whitehead contends that the human way of understanding existence as a unity of interlocking and interdependent <WSD>processes</WSD> which constitute each other and which cause each other to be and not to be is possible only because the basic form of such an understanding , for all its vagueness and tendency to mistake the detail , is initially given in the way man feels the world . 
Meaning of the word marked with <WSD> tags:  (psychology) the performance of some composite cognitive activity; an operation that affects mental contents