HOW SCIENCE SHOULD BE REGARDED. 165 



progress, and the relations of its parts to each other. 

 There must be serious incompleteness in any history of the 

 sciences, which, leaving out of view the first steps of their 

 genesis, commences with them only when they assume defi 

 nite forms. There must be grave defects, if not a general 

 untruth, in a philosophy of the sciences considered in their 

 interdependence and development, Avhich neglects the in 

 quiry how they came to be distinct sciences, and how they 

 were severally evolved out of the chaos of primitive ideas. 

 Not only a direct consideration of the matter, but all 

 analogy, goes to show that in the earlier and simpler stages 

 must be sought the key to all subsequent intricacies. The 

 time was when the anatomy and physiology of the human 

 being were studied by themselves when the adult man 

 was analyzed and the relations of parts and of functions 

 investigated, without reference either to the relations ex 

 hibited in the embryo or to the homologous relations exist 

 ing in other creatures. Now, however, it has become 

 manifest that no true conceptions, no true generalizations, 

 are possible under such conditions. Anatomists and phys 

 iologists now find that the real natures of organs and tis 

 sues can be ascertained only by tracing their early evolu 

 tion ; and that the affinities between existing genera can 

 be satisfactorily made out only by examining the fossil gen- 

 jera to which they are allied. Well, is it not clear that the 

 (Ilike must be true concerning all things that undergo devel- 

 lopment ? Is not science a growth ? Has not science, too, 

 | its embryology ? And must not the neglect of its embry 

 ology lead to a misunderstanding of the principles of its 

 evolution and of its existing organization ? 



There are a priori reasons, therefore, for doubting the 

 truth of ah 1 philosophies of the sciences which tacitly pro 

 ceed upon the common notion that scientific knowledge 

 and ordinaiy knowledge are separate ; instead of com 

 mencing, as they should, by affiliating the one upon the 



