The audacity of my enterprise really consists in my attempting to act according to this general truth in a particular case — the case, that is, of the phenomena of animal life. I have gone on the assumption that knowledge of animal chemistry, for example, at one extreme, and of human consciousness at the other, would be simple blanks as to meaning but for the relation of the two knowledges to each other and to still more general knowledge of animal life.  

Could we imagine a chimpanzee possessed of as much laboratory knowledge of organic chemistry as an Emil Fischer, that knowledge would be really meaningless were the creature's mind that of a chimpanzee in all other respects.  

A systematic defense of a conception of zoology based on a general theory of natural knowledge such as this, can not, of course, be thought of in a preface. Indeed, such a conception can not be fully justified by any argument merely for it.  

 The justification must be found largely in a worked-out application of the conception itself. In other words, the very fabric of this book must be the chief justification sought.