CHAPTER IV. 



PRESUPPOSITIONS OF INDUCTION: UNIFORMITY OF 

 NATURE. 



223. INTERPRETATIONS OF THE PRINCIPLE OF UNIFORMITY 

 IN NATURE. In the preceding chapter attention was called to 

 two principles presupposed by induction : &quot; sufficient reason &quot; 

 and &quot;causality&quot;. There is another principle which it postulates 

 still more directly and explicitly, the Uniformity of Nature. The 

 aim of induction being to reach as far as may be general truths 

 or laws about certain domains of our experience, it does and must 

 assume in a special way that the agencies which it studies be uni 

 form in their modes of operation throughout space and time. Only 

 in so far forth as these agencies act regularly, uniformly, will our 

 generalizations about them be reliable. About what is variable, 

 unstable, capricious, we can make no certain or scientific general 

 statement. 1 We can have science only of what is orderly and 

 amenable to law. Therefore, underlying the inductive process by 

 which we establish general laws of nature, there is the postulate 

 known as the uniformity of nature. It has been stated in many 

 alternative ways by logicians, philosophers, and scientists, the most 

 usual formula, perhaps, being this one : &quot; The same physical causes, 

 acting in similar circumstances, produce similar results &quot;. 2 There 

 has also been much discussion about its precise import and rela 

 tion to induction, about the origin of our belief in it, and the 

 grounds on which we yield it our assent. 



Before examining these questions, a word about the sphere of 

 application of the principle may not be out of place. Strictly 



1 c/. JOSEPH, op. cit., p. 374. 



2 Compare the formula of Duns Scotus : &quot; Whatever has resulted regularly and 

 constantly from the action of a non-free cause cannot be due to chance, but must be 

 connected with the nature of that cause, and will therefore always result from it &quot; 

 (supra, 208). Other alternative statements are : &quot; Nature is uniform in its mode of 

 action &quot; ; &quot; the future will resemble the past &quot; ; &quot; the unobserved will resemble the ob 

 served&quot; ; &quot; the unknown will resemble the known &quot; (cf. VENN, op. cit., pp. 119 sqq.). 



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