296 THE EVOLUTION OF SCIENTIFIC THEORIES 



difference is observed between the model and scientific practice, this 

 is to be regarded as a criticism of scientific practice, and not of the 

 model. 



Cherishing the ideal of a tidy, complete, and definitive account of 

 some organism, one might think to confine himself to a careful analy- 

 sis of its skeletal remains— leaving out of all account the complex, con- 

 fusing, and "untidy" activities of the living flesh. But we never de- 

 lude ourselves that palaeontology is a complete biology. That logical 

 analysis of completed scientific theories offers a complete philosophy 

 of science is a delusion no better founded. Indeed, if we confine our- 

 selves to logical analysis of finished structures, our understanding 

 must forever rest incomplete simply because we cannot then under- 

 stand why those structures are what they are. Poincare emphasizes 

 that this consideration applies even to the purely formal discipline 

 of mathematics— and he drives his point home with the metaphor of 



. . . those delicate assemblages of silicious needles which form the 

 skeleton of certain sponges. When the organic matter has disap- 

 peared, there remains only a frail and elegant lace-work. True, noth- 

 ing is there except silica, but what is interesting is the form this silica 

 has taken, and we could not understand it if we did not know the 

 living sponge which has given it precisely this form. 



The logician's dream of a definitive philosophy of science is nothing 

 but a dream. Through the mesh of epistemologic analyses, conducted 

 exclusively in the hypothetically distinct "context of justification," 

 slips all that makes science what it is: a unique enterprise best char- 

 acterized by tliat extraordinary dynamism of which I have sought to 

 render just account. 



