SCIENCE AND DEMONSTRATION 237 



other already known laws. 1 For instance, the law that de 

 scribes the path of a projectile as a parabola expresses the com 

 bined effects of the initial motion and of gravitation, acting 

 simultaneously. The law that rocks and mountains are disinte 

 grated by frost succeeding rain, is an expression of the joint 

 effect of causes acting successively, each according to already 

 known laws of its own. Or (2) we may be able to connect the 

 law in question with other known laws showing them to be all 

 special applications of some wider and more general law. Thus, 

 the law of gravitation connected and &quot; explained &quot; the laws of 

 falling bodies and the laws of the revolving planets. We have 

 already met numerous other examples of explanation ; and when 

 dealing with hypothesis and causation we discussed the nature 

 of the limitations within which phenomena can be &quot; explained &quot;. 

 It is sometimes stated that Aristotle s conception of science 

 is entirely different from the modern conception. But apart 

 from the fact that inductively established laws and their appli 

 cations, which are nowadays universally regarded as &quot; scientific,&quot; 

 would not be so regarded by Aristotle the difference really lies 

 only in the terminology. He conceived science, after the manner 

 of geometry, as starting from the definition, which reveals the 

 essence of the &quot;kind,&quot; and demonstrating the properties deriv 

 able from the latter. His theory of the specific type or form, 

 as embodied in the individuals and forming their essence, 

 was copiously illustrated by examples drawn from the domain of 

 biology. But it is not so easy to distinguish the attributes that 

 are essential to an organic type from the properties of the latter, 

 as it is to distinguish between the essence or definition of a 

 triangle and its properties. And the same difficulty prevails in 

 all the sciences which deal with concrete, actually existing things. 

 Hence, in these sciences, &quot; for definition such as we have it in 

 geometry, we must substitute classification ; and for the demon 

 stration of properties, the discovery of laws. A classification 

 attempts to establish types ; it selects some particular character 

 istics as determining the type of any species. ... It will be the 

 description of the type, drawn up on such principles as these, 

 that will serve for definition &quot;. 2 Obviously, there is no change 

 of ideal in substituting classification for definition ; our aim in 

 classification is to reach definitions of real kinds of things. So, 



1 C/. MELLONE, op. tit., pp. 328 sqq. ; JOSEPH, op. cit., pp. 474 sqq. 



2 JOSEPH, op. cit., p. 89. Cf. supra, 47, 66. 



