XII. Of the Transformation of Hypotheses in the History of Science. 

 By W. Whewell, D.D., Master of Trinity College. 



[Eead May 19, 1851.] 



1. The history of science suggests the reflection that it is very difficult for the same per- 

 son at the same time to do justice to two conflicting theories. Take for example the Cartesian 

 hypothesis of vortices and the Newtonian doctrine of universal gravitation. The adherents of 

 the earlier opinion resisted the evidence of the Newtonian theory with a degree of obstinacy 

 and captiousness which now appears to us quite marvellous : while on the other hand, since 

 the complete triumph of the Newtonians, they have been unwilling to allow any merit at all 

 to the doctrine of vortices. It cannot but seem strange, to a calm observer of such changes, 

 that in a matter which depends upon mathematical proofs, the whole body of the mathematical 

 world should pass over, as in this and similar cases they seem to have done, from an opinion 

 confidently held, to its opposite. No doubt this must be, in part, ascribed to the lasting 

 effects of education and early prejudice. The old opinion passes away with the old genera- 

 tion : the new theory grows to its full vigour when its congenital disciples grow to be masters. 

 John Bernoulli continues a Cartesian to the last ; Daniel, his son, is a Newtonian from the 

 first. Newton's doctrines are adopted at once in England, for they are the solution of a pro- 

 blem at which his contemporaries have been labouring for years. They find no adherents in 

 France, where Descartes is supposed to have already explained the constitution of the world ; 

 and Fontenelle, the secretary of the Academy of Sciences at Paris, dies a Cartesian seventy 

 years after the publication of Newton's Principia. This is, no doubt, a part of the explana- 

 tion of the pertinacity with which opinions are held, both before and after a scientific revolu- 

 tion : but this is not the whole, nor perhaps the most instructive aspect of the subject. There 

 is another feature in the change, which explains, in some degree, how it is possible that, in 

 subjects, mainly at least mathematical, and therefore claiming demonstrative evidence, mathe- 

 maticians should hold different and eVen opposite opinions. And the object of the present 

 paper is to point out this feature in the successions of theories, and to illustrate it by some 

 prominent examples drawn from the history of science. 



2. The feature to which I refer is this ; that when a prevalent theory is found to be unte- 

 nable, and consequently, is succeeded by a different, or even by an opposite one, the change is 

 not made suddenly, or completed at once, at least in the minds of the most tenacious adherents 

 of the earlier doctrine ; but is effected by a transformation, or series of transformations, of the 

 earlier hypothesis, by means of which it is gradually brought nearer and nearer to the second ; 

 and thus, the defenders of the ancient doctrine are able to go on as if still asserting their first 

 opinions, and to continue to press their points of advantage, if they have any, against the new 

 theory. They borrow, or imitate, and in some way accommodate to their original hypothesis, the 

 new explanations which the new theory gives, of the observed facts ; and thus they maintain a 



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