THEORIES OF SCIENTIFIC CONCEPTS 161 



routes, recover the events which were thus operated upon; 

 hence there is some justification for saying that scientific 

 concepts still have applicability to events. But in conven- 

 tionalism this applicability has been more or less completely 

 lost. One does not, strictly speaking, derive his concepts at 

 all. He is tempted to say that he creates them. Yet this is 

 not quite true; conventionalism does not reduce to nominal- 

 ism. It insists that scientific symbols of this particular kind are 

 suggested by the data, but that they are given meaning through 

 elaborate mental operations. The extent and importance of 

 these operations are demonstrated by the fact that the symbols 

 thus devised can no longer be spoken of as true or false, but 

 must be characterized as convenient or inconvenient. 



Quotations from Henri Poincare will illustrate the partic- 

 ular way in which he develops this position. While he admits 

 that there are to be found in science not only empirical 

 laws, i.e., descriptive generalizations, but also hypotheses in 

 the ordinary sense, i.e., imaginative notions which can be 

 verified and falsified, he nevertheless insists that the most 

 important kinds of symbol are those which — mistakenly 

 called "hypotheses" — are more properly characterized as 

 "disguised definitions," or "conventions." The best ex- 

 amples of them are to be found in the principles of geometry 

 and of mechanics. They are like laws in that they have 

 their foundation in experience, but they are different from 

 laws in that they are not dictated by data. "We see that 

 experience plays an indispensable role in the genesis of 

 geometry; but it would be an error thence to conclude that 

 geometry is, even in part, an experimental science. . . . 

 If it were experimental . . . geometry would be only the 

 study of the movements of solids; but in reality it is not 

 occupied with natural solids, but has for object certain ideal 

 solids, absolutely rigid, which are only a simplified and very 

 remote image of natural solids. . . . Experience guides us 

 in this choice without forcing it upon us." 1 In the same 



1 Foundations of Science (New York: Science Press, 1921), p. 79. This is his 

 Science and Hypothesis, Value of Science, and Science and Method bound in a single 

 volume. 



