460 OPEKATIONS SUBSIDIARY TO INDUCTION, 



tance. If, for instance, we only compare animals according to their color, 

 and class those together which are colored alike, we form the general con- 

 ceptions of a white animal, a black animal, etc., which are conceptions le- 

 gitimately formed ; and if an induction were to be attempted concerning 

 the causes of the colors of animals, this comparison would be the proper 

 and necessary preparation for such an induction, but would not help us to- 

 ward a knowledge of the laws of any other of the properties of animals ; 

 while if, with Cuvier, we compare and class them according to the struc- 

 ture of the skeleton, or, with Blainville, according to the nature of their 

 outward integuments, the agreements and differences which are observable 

 in these respects are not only of much greater importance in themselves, 

 but are marks of agreements and differences in many other important par- 

 ticulars of the structure and mode of life of the animals. If, therefore, the 

 study of their structure and habits be our object, the conceptions gener- 

 ated by these last comparisons are far more " appropi-iate " than those gen- 

 erated by the former. Nothing, other than this, can be meant by the ap- 

 propriateness of a conception. 



When Dr. Whewell says that the ancients, or the school-men, or any 

 modern inquirers, missed discovering the real law of a phenomenon because 

 they applied to it an inappropriate instead of an appropriate conception; 

 he can only mean that in comparing various instances of the phenomenon, 

 to ascertain in what those instances agreed, they missed the important 

 points of agreement; and fastened upon such as were either imaginary, 

 and not agreements at all, or, if real agreements, were comparatively tri- 

 fling, and had no connection with the phenomenon, the law of which was 

 sought. 



Aristotle, philosophizing on the subject of motion, remarked that certain 

 motions apparently take place spontaneously; bodies fall to the ground, 

 flame ascends, bubbles of air rise in water, etc. ; and these he called nat- 

 ural motions ; while others not only never take place without external in- 

 citement, but even when such incitement is applied, tend spontaneously to 

 cease ; which, to distinguish them from the former, he called violent mo- 

 tions. Now, in comparing the so-called natural motions with one another, 

 it appeared to Aristotle that they agreed in one circumstance, namely, that 

 the body which moved (or seemed to move) spontaneously, was moving 

 toward its own place ; meaning thereby the place from whence it originally 

 came, or the place where a great quantity of matter similar to itself was 

 assembled. In the other class of motions, as when bodies are thrown up in 

 the air, they are, on the contrary, moving from their own place. Now, 

 this conception of a body moving toward its own place may justly be con- 

 sidered inappropriate ; because, though it expresses a circumstance really 

 found in sonje of the most familiar instances of motion apparently spon- 

 taneous, yet, first, there are many other cases of such motion, in which that 

 circumstance is absent ; the motion, for instance, of the earth and planets. 

 Secondly, even when it is present, the motion, on closer examination, would 

 often be seen not to be spontaneous ; as, when air rises in water, it does 

 not rise by its own nature, but is pushed up by the superior weight of the 

 water which presses upon it. Finally, there are many cases in which the 

 spontaneous motion takes place in the contrary direction to what the theory 

 considers as the body's own place ; for instance, when a fog rises from a 

 lake, or when water dries up. The agreement, therefore, which Aristotle 

 selected as his principle of classification, did not extend to all cases of the 

 phenomenon he wanted to study, spontaneous motion; while it did include 



