138 INTRODUCTION TO PHILOSOPHY OF SCIENCE 



if the former 'pulls' more than the latter when they are 

 unsupported; object P is softer than object Q if a given 

 force makes a deeper impression on P than on Q; object X 

 is moving faster than object Y if they are placed in a race 

 and object X reaches a certain point before object Y. 

 Measuring techniques are essentially the continuation of 

 this process in the direction of greater refinement. Elaborate 

 measurement techniques will presumably not be found in 

 purely descriptive sciences, for these are often founded upon 

 hidden correlations, as in the case of the measurement of 

 heat by the expansion of a column of mercury, and in the 

 case of the measurement of weight by the distortion of a 

 coiled spring. 



(4) The correlational features of descriptive science con- 

 stitute its most distinctive properties. "Things are correlated 

 (con, relata) when they are so related or bound to each other 

 that where the one is the other is, and where one is not the 

 other is not. ... In geometry the occurrence of three 

 equal angles in a triangle is correlated with the existence 

 of three equal sides; in physics gravity is correlated with 

 inertia; in botany exogenous growth is correlated with the 

 possession of two cotyledons, or the production of flowers 

 with that of spiral vessels." 1 But the correlations here used 

 for illustrative purposes are not such as are found in em- 

 pirical science. Descriptive science asserts not universal 

 laws but merely enumerative generalizations. Often these 

 correlations are merely statistical in character. The cau- 

 tious attitude which is characteristic of science at this stage 

 does not permit rash generalization. Laws are asserted 

 only over the range of examined cases. Descriptive anthro- 

 pology avoids extending to society as a whole customs of 

 monogamous marriage found only in a limited group ; biology 

 refuses to apply the principles of sexual generation to the 

 organic world as a whole on the basis of its apparent omni- 

 presence in the higher living forms. Correlations in descrip- 

 tive science are properly stated in the form of frequencies. 



1 W. S. Jevons, Principles of Science, p. 681. 



