THEORIES AND MODELS 223 



That we can imagine such a process, and have a name for it, does 

 not of course ensure its existence. Admittedly, Newton implies that 

 his theoretic postulates were obtained "by induction." But, after more 

 than a quarter of a millennium, we have yet to discover a formal 

 method competent to produce, from Newton's data, Newton's con- 

 cepts and postulates. We observe, too, that the Newtonian postulate 

 of universal gravitation was denounced by Leibniz, and others no 

 fools, as a reprehensible relapse back to invocation of an occult in- 

 fluence as "explanation" of physical appearances. That one man's 

 "induction" should be another man's occultism perhaps suggests that 

 induction involves rather more than formally correct reasoning. 

 Logicians still write books on induction a century after Bernard 

 correctly noted its supra-logical character: 



When we believe we advance from a particular case to a principle— 

 that is, when we proceed inductively— we really deduce; the experi- 

 menter lets himself be guided by a principle supposed to be pro- 

 visional, which he modifies at every instant while he searches in more 

 or less darkness. 



Logic and mathematics sustain the deductive operation, but are 

 powerless to produce the provisional hypotheses on which all else 

 depends. Such an idea as universal gravitation is not derived but in- 

 vented! How? Is it not the same Newton that preaches the cautious 

 virtue of induction who also says: 



No great discovery is ever made without a bold guess. 



"Induction" involved with guessing? What a fall! But, when one 

 comes to think about it, our naive concept of a formal method of in- 

 duction cannot but seem absurd, irretrievably negated by experience 

 that, as Cohen points out, is immediately accessible to each among us. 



... it is often claimed that the various canons of induction tell us 

 how to discover the causes of phenomena. The reader can readily test 

 this claim by applying these canons to discover some causes not yet 

 known to him, e.g., the cause of cancer, . . . 



In general, there is no definite method of discovering new truth, 

 . . . The discovery of what has hitherto been unknown involves a 

 leap into the dark, and the tragic history of human failure to solve 

 our vital problems shows how real is the darkness. 



