REPLIES TO THE QUARTERLY REVIEWERS. 551 



the authority of Prof. Tait, illustrates in Physics that same error of 

 the inductive philosophy which, in Metaphysics, I have pointed out 

 elsewhere (" Principles of Psychology," Part VIL). It is a doctrine 

 implying that we can go on forever asking the proof of the proof, 

 without finally coming to any deepest cognition which is unproved 

 and unprovable. That this is an untenable doctrine I need not say 

 more to show. Nor, indeed, would saying more to show it be likely 

 to have any effect, in so far at least as the reviewer is concerned ; see- 

 ing that he thinks I am " ignorant of the very nature of the principles " 

 of which I am speaking, and seeing that my notions of scientific rea- 

 soning "remind" him "of the Ptolemists," who argued that the 

 heavenly bodies must move in circles because the circle is the most 

 perfect figure. 1 



Not to try the reader's patience further, I will end by pointing out 

 that, even were the reviewer's criticisms all valid, they would leave 

 unshaken the system he contends against. Though one of his sen- 

 tences (page 480) raises the expectation that he is about to assault, 

 and greatly to damage, the fabric of propositions contained in the 

 second part of " First Principles," yet all those propositions which 

 constitute the fabric he leaves not only uninjured but even untouched, 

 contenting himself with trying to show (with what success we have 

 seen) that the fundamental one is an a posteriori truth, and not an 

 a priori truth. Against the general Doctrine of Evolution, considered 

 as an induction from all concrete phenomena, he utters not a word ; 

 nor does he utter a word to disprove any one of those laws of the re- 

 distribution of matter and motion by which the process of Evolution 

 is deductively interpreted. Respecting the law of the Instability of 

 the Homogeneous, he says no more than to quarrel with one of the 

 illustrations. He makes no criticism on the law of the Multiplication 

 of Effects. The law of Segregation he does not even mention. Nor 

 does he mention the law of Equilibration. Further, he urges nothing 

 against the statement that these general laws are severally deducible 

 from the ultimate law of the Persistence of Force. Lastly, he does 

 not deny the Persistence of Force, but only differs respecting the na- 



1 Other examples of these amenities of controversy, in which I decline to imitate my 

 reviewer, have already been given. What occasions he supplies me for imitation, were I 

 minded to take advantage of them, an instance will show. Pointing out an implication 

 of certain reasonings of mine, he suggests that it is too absurd even for me to avow ex- 

 plicitly, saying: "We scarcely think that even Mr. Spencer will venture to claim as a 

 datum of consciousness the Second Law of Motion, with its attendant complexities of 

 component velocities," etc. Now, any one who turns to Newton's " Principia " will find 

 that to the enunciation of the Second Law of Motion nothing whatever is appended but 

 an amplified restatement — there is not even an illustration, much less a proof. And 

 from this law, this axiom, this immediate intuition or " datum of consciousness," Newton 

 proceeds forthwith to draw those corollaries respecting the composition of forces which 

 underlie all dynamics. What, then, must be thought of Newton, who explicitly assumes 

 that which the reviewer thinks it absurd to assume implicitly ? 



