282 PETER GUTHRIE TAIT 



Tait had torn a sentence from its context (no doubt in imitation of Spencer's 

 own method of quotation), and maintained that the unknown quantity was 

 the application of Tail's story. It should be remembered of course that 

 Spencer had been arguing in his First Principles and in his Replies to 

 Criticisms that Newton's Laws of Motion were known it priori, whereas 

 Tait regarded the Properties of Matter, including the Laws of Motion, as 

 unknown until they were discovered by the legitimate methods of experience, 

 and by these alone. (See also Tail's reply, p. 285 below.) 



This passage at arms excited a great deal of interest among the students 

 of the Physical Laboratory. One of our number was R. B. Haldane 1 , 

 second to none in knowledge of philosophy and in power of debate. We 

 fought the Spencer-Tait controversy over and over again. I remember that 

 W. K. Clifford visited Edinburgh about that time, and in the Tea Room at 

 one of the April Meetings of the Royal Society of Edinburgh much lively 

 talk went on regarding the controversy. Tait was in great spirits and said 

 to Clifford, " There is not a man in England I suppose, other than Herbert 

 Spencer, who does not see the point of my story." Clifford responded 

 with a hearty laugh, "No doubt, it is a very good story." 



In the same reply of April 2, Spencer practically reproduced the argument 

 as given in his pamphlet, and made the remark that Tait himself, 



" by saying of physical axioms that the appropriately-cultivated intelligence sees 

 at once their necessary truth, tacitly classes them with mathematical axioms, of which 

 this self-evidence is also the recognised character." 



Writing to the same number of Nature the British Quarterly Reviewer 

 disposed of Spencer's claim that he knew what Newton thought by quoting 

 from two letters in which Newton wrote to Cotes in these words : 



" In experimental philosophy it (i.e. hypothesis) is not to be taken in so large a 

 sense as to include the first Principles or Axiomes which I call the Laws of Motion. 

 These Principles are deduced from phenomena and made general by Induction, 

 %vhich is the highest evidence that a Proposition can have in this Philosophy"... 



" On Saturday last I wrote you representing that Experimental philosophy 

 proceeds only upon phenomena and deduces general Propositions from them only by 

 Induction. And such is the proof of mutual attraction. And the arguments for 

 the impenetrability, mobility, and force of all bodies, and for the laws of motion are 

 no better." 



On April 1 6, Herbert Spencer so far admitted his imperfect knowledge, 

 and withdrew his contention that Newton regarded the Laws of Motion as 

 axioms in the limited sense for which he had been all along arguing ; but he 



1 Secretary of State for War since 1905. 



