814 



SCIENCE. 



[N. S. Vol. III. No. 74. 



cocksureness there displaj^ed, nor is the re- 

 viewer vindicated in his certainty that the au- 

 thor intended to force a ' psj'chological connec- 

 tion ' here, or ought to have made out one 

 there. If Dr. Boas, remembering that all 

 writers have not reached that eminence of 

 synthesis and systematization on which he so 

 conspicuously dwells, will once more peruse the 

 the volume he will discover that neither in its 

 claims nor in its execution does it traverse those 

 sound principles of the comparative method of 

 which a peculiar interpretation belongs to him. 

 In these the writer believes as thoroughly as 

 does the reviewer. But, as to the exact man- 

 ner and method of determining where a ' psy- 

 chological connection ' exists, or what pheno- 

 mena are ' derived psychologically or his- 

 torically from common causes, ' a great deal of 

 reasonable difference in opinion exists, and this 

 the author has not ignored. The reviewer has 

 throughout attributed to the writer a much 

 more ambitious thesis than he really attempted, 

 and has apparently seen efforts at connection 

 and comparison where none such existed or 

 were thought of. That the author has com- 

 pleted the task he set himself, other reviewers 

 have perceived and acknowledged ; to have ac- 

 complished the task the reviewer sets him, he 

 had needs be the reviewer himself 



Alex. F. Chamberlain. 

 WoECESTEE, Mass., May 15, 1896. 



' THAT GREAT LAW OF LOGIC. ' 



In a recent number of this Journal (p. 668 

 above) I ventured to criticise Professor Brooks 

 for using ambiguously the phrase ' test of 

 truth,' and for not appreciating the force of a 

 letter by M. M., calling attention to this. I 

 then pointed out what seemed to me an analo- 

 gous confusion in regard to the material and the 

 efiicient causes of evolution, saying that I did 

 this at the risk of being accused of irrelevancy 

 by Professor Brooks. I did not at all intend to 

 include Professor Brooks with those who have 

 confused material and efficient causes, and his 

 reply (p. 779 above) should have been directed 

 to Professor Cunningham who in the May num- 

 ber of Natural Science makes, I think incor- 

 rectly, this charge. 



Professor Brooks is mistaken in saying that I 



did not specify anyone who seems to me to use 

 the word ' cause ' ambiguously. It is, indeed, 

 easy to adduce other eminent naturalists in ad- 

 dition to the one to whom I referred. Thus Pro- 

 fessor Weismaun writes in his most recent paper 

 {On Germinal Selection, authorized translation : 

 Chicago, 1896): "The protective coloring 

 * * * * arose not because it was a constitu- 

 tional necessity of the animal's organism that 

 here a red and there a white, black, or yellow 

 spot should be produced, but because it was ad- 

 vantageous, because it was necessary for the 

 animal." Weismann's state of mind seems to 

 be similar to that of the little boy who was 

 watching at a hole for a woodchuck to come 

 out, and when asked how he knew there was a 

 woodchuck in the hole said ' ' because we have 

 company for dinner and there is no meat in the 

 house." 



While Professor Brooks replies to a question in 

 which we agree he neither defends nor re- 

 tracts the statement which I think is guilty of 

 an analogous blunder, and it seems as though 

 he does not appreciate the point raised bj' M. 

 M. It is, perhaps, merely a matter of words, 

 but when words are used ambiguously argu- 

 ments become fallacious. When Professor Brooks 

 writes advocating ' ' that great law of logic, 

 ' the test of truth is evidence and not conceiv- 

 ability,' " does he mean to deny that conceiv- 

 ability is a sufficient proof of truth or to denj^ 

 that conceivability is a necessary condition of 

 truth, and what does he mean by conceiv- 

 ability ? 



In the curious history of thought we have 

 had inconceivability urged as a proof of truth, 

 but not, so far as I am aware, conceivability ; 

 no one holds that the situations in the mod- 

 ern realistic novel have occurred because they 

 are conceivable. It has, however, been claimed 

 that conceivability is a necessary condition of 

 truth, and by one M'ho holds this j)osition (as Mr. 

 Herbert Spencer) Professor Brooks' statement 

 could neither be affirmed nor denied any more 

 than he could answer yes or no to the question 

 "Did you hold the lantern when your father 

 robbed the stagecoach ? ' ' 



Then Professor Brooks' ' great law of logic ' 

 is doubly illogical because he also uses the word 

 ' conceivabilitj' ' ambiguously. When he writes 



