Dr. WHEWELL'S CRITICISM OF ARISTOTLE'S ACCOUNT OF INDUCTION. 69 



that Mars moves elliptically was proved to be true. But still, there was the question, Is it 

 convertible ? Do all the planets move as Mars moves ? This was proved, (suppose,) to be 

 true, for the Earth and Venus. But still the question remains, Do all the planets move as 

 Mars, Earth, Venus, do ? The inductive generalizing impulse boldly answers, Yes, to this 

 question ; though the rules of Syllogism do not authorize the answer, and though there 

 remain untried cases. The inductive philosopher tries the cases as fast as they occur, in 

 order to confirm his previous conviction ; but if he had to wait for belief and conviction till 

 he had tried every case, he never could have belief or conviction of such a proposition at all. 

 He is prepared to modify or add to his inductive truth according as new cases and new 

 observations instruct him ; but he does not fear that new cases or new observations will 

 overturn an inductive proposition established by exact comparison of many complex and 

 various phenomena. 



Aristotle's example offers somewhat similar reflections. He had to establish a proposition 

 concerning long-lived animals, which should be true, and should be susceptible of generalized 

 conversion. To prove that the elephant, horse, and mule are destitute of gall-bladder required, 

 at least, the labour of anatomizing those animals in the seat of that organ. But this labour was 

 not enough ; for he would find those animals to agree in many other things besides in being 

 acholous. He must have selected that character somewhat at a venture. And the guess was 

 wrong, as a little more labour would have shewn him ; if for instance, he had dissected deer : 

 for they are acholous, and yet short-lived. A trial of this kind would have shewn him that the 

 extreme term, acholous, did extend beyond the mean, namely, animals such as elephant, horse, 

 mule ; and therefore, that the conversion was not allowable, and that the Induction was unten- 

 able. In truth, there is no relation between bile and longevity*, and this example given by 

 Aristotle of generalization from induction is an unfortunate one. 



In discussing this passage of Aristotle, I have made two alterations in the text, one of which 

 is necessary on account of the fact ; the other on account of the sense. In the received text, 

 the particular examples of long-lived animals given are man, horse, and mule (e'd>' w $e F, to 

 KaOeKacrToi' naicfjofiiov, otov avOpunrov, K.CU iiriro's, icai >}/Uioi/os). And it is afterwards said that all 

 these are acholous : (d\\a Kal to B, to fjni] e^ov yo\riv, wavri inrdpyei t«S T.) But man has a 

 gall-bladder: and the fact was well known in Aristotle's time, for instance, to Hippocrates; so 

 that it is not likely that Aristotle would have made the mistake which the text contains. But 

 at any rate, it is a mistake ; if not of the transcriber, of Aristotle ; and it is impossible to 

 reason about the passage, without correcting the mistake. The substitution of e\e(pa<i for 

 avOpwiros makes the reasoning coherent ; but of course, any other acholous long-lived animal 

 would do so equally well. 



• Sir Owen, to whom I am indebted for the physiological 

 part of this criticism, tells me, "All mammalia have bile, the 

 carnivora in greater proportion than the herbivora: the gall- 

 bladder is a comparatively unimportant accessory to the biliary 

 apparatus ; adjusting it to certain modifications of stomach and 



intestine : there is no relation between natural longevity and 

 bile. Neither has the presence or absence of the gall-bladder 

 any connexion with age. Man and the elephant are perhaps 

 for their size the longest lived animals, and the latest at coming 

 to maturity : one has the gall-bladder, and the other not." 



