14 THE THEORY OF [pt. 



Far different is the account of itself which science has since learned 

 to give. But this change of attitude is not a revolt against thought 

 as such, or against reason as such ; it is only a loss of belief in the 

 literal inspiration of the formulae proper to science. It would be just 

 as extravagant to claim that the scientific investigator of the twentieth 

 century sets down absolute truths in his laboratory notebook, and, 

 armed with an infallible method, explores the real structure of an 

 objective world, as it would be fantastic to claim that Jehovah 

 dictated an absolute code of the good to Moses on Mount Sinai. To 

 say that the development of a living being can best be described in a 

 metrical or mechanical way is not to say that it is metrical or me- 

 chanical and nothing else. The physico-chemical embryologist is not 

 committed to any opinion on what his material really is, but he is 

 committed to the opinion that the scientific method is one way of 

 describing it, and that it is best to apply that method in its full rigour 

 if it is to be applied at all. In other words, following the train of 

 thought of William James, he does not assert that the courts of Heaven 

 as well as those of our laboratories resound with expressions such as 

 "organisers of the second grade," and "so many milHgrams per cent." 

 The mechanical theory of the world, which is, as many beHeve, 

 bound up indissolubly with one of the ultimate types of human 

 experience, can no longer be considered as necessarily involving the 

 exclusion of other theories of the world. Or, put in another way, it 

 is a theory of the world, and not a pocket edition of the world itself 



But before bringing forward any arguments in support of this 

 attitude and in defence of physico-chemical embryology, it will be 

 well to consider briefly those theoretical tendencies in modern biology 

 which go together under the inexact adjective "neo-vitalistic", for 

 their influence in scientific thought has been far-reaching. To deal 

 critically with them is not a waste of time, for, were we to adopt 

 any one of them, we should find that the notion of embryology as 

 complicated biophysics and biochemistry would have to be abandoned, 

 and quite other means of approach (never, indeed, very well defined) 

 would have to be used. 



The Stumbling-block of Hormism 



Hormism, or "Psychobiology," may be dealt with in a few 

 words. Chiefly supported by A. Wagner in Germany, and by 

 E. S. Russell and L. T. Hobhouse in this country, it holds that — to 





