CRITICISMS CORRECTED. 395 



tions of space " '? Not a thing, or a force, but a laio. What is the 

 law here said to be knowable a priori ? The law of variation of any 

 or every central force. And what is alone included in the assertion of 

 this a 2yriori law ? Simply this, that given a central force, and such is 

 the law according to which it will vary. Nothing is alleged respecting 

 the existence of any central force. Does Professor Birks contend that 

 if I say that light, proceeding from a center, necessarily varies in- 

 versely as the square of the distance, I thereby say that the existence 

 of light itself is known a priori as a result of space relations ? When 

 I assert that of the heat radiating in all directions from a point, the 

 quantity falling on a given surface necessai'ily decreases as the square 

 of the distance increases, do I thereby assert the necessary existence 

 of the heat which conforms to this law ? Why then do I, in asserting 

 that the laio of variation of gravity " results by a fatal necessity from 

 the laws of space" simultaneously assert that ^^gravitation results by 

 a fatal necessity from the laws of space " ? Professor Birks, however, 

 because I assert the first says I assert the second. My proposition. 

 Central forces vary inversely as the squares of the distances, he actually 

 transforms into the proposition. There is a cosmical force which varies 

 inversely as the squares of the distances ; and debiting me with the 

 last as identical with the first, proceeds, after his manner, to debit me 

 with various resulting absurdities. 



Having thus shown that the j^assage in question contains no such 

 statement as that which Pi'ofessor Birks says it contains, I go on to 

 show that I have not removed this passage because I have abandoned 

 the belief it embodies. Clear proof is at hand. If Professor Birks 

 will turn to the " Replies to Criticisms " contained in the third volume 

 of my "Essays : Scientific, Political, and Speculative" (pp. 334-337), 

 he will find that I have there defended the above proposition against 

 a previous attack ; and assigning, as I have done, justification for 

 it, I have shown no sign of relinquishing it. Why, then, Professor 

 Birks will ask, did I make the change in question ? Had his mental 

 attitude been other than it is, he might readily have divined the rea- 

 son. Knowing, as he seemingly does, that this doctrine which he 

 criticises had been already criticised in a similar manner (for other- 

 wise he would scarcely have discovered the change I have made), 

 he might have seen clearly enough that the passage was suppressed 

 simply to deprive opponents of the opportunity of evading the gen- 

 eral argument of the chapter by opening a side issue on a point not 

 essential to its argument. 



The chapter has for its subject, certain incapacities of the human 

 mind a subject, by the way, on which theologians are never tired 

 of enlarging when it suits their own purpose, but on which an antag- 

 onist may not enlarge without exciting their anger. Various examples 

 of these incapacities are given, to justify and enforce the conclusion 

 drawn. Among these was originally included the example in ques- 



