SCIENCE. 



[N. S. Vol. XV. No. 378. 



and equally instructive, revelations of the 

 inexhaustible variety of nature. We talk 

 about humanity, but we know and deal 

 with Peter and Henry and Thomas and 

 Black Jim and Yellow John. We need 

 proper names for all the animals that we 

 are well acquainted with. The zoologist 

 tells us about the genus Equus, but if he 

 has any practical dealings with horses, he 

 never says one horse is the same as another, 

 or even that a horse is the same to-day as 

 he was yesterday, for even if he be neither 

 sick nor lame nor hungry, he is one day 

 nearer the end of his usefulness. 



The botanist talks learnedly of Chrysan- 

 themum indicum, but the florist sells gold- 

 en wedding and ivory and fair dawn and 

 snow queen and hundreds of others. For 

 many scientific purposes it is necessary to 

 give proper names, or designating num- 

 bers, to seedling plants, and it may be that 

 if the chemist were dealing with individ- 

 uals, instead of averages, he might need 

 proper names to tell to others his discov- 

 eries about molecules and atoms. 



14. Are identity and diversity absolute 

 or relative? 



To-day's sun is the same as yesterday's, 

 yet the changes which go on in the sun, 

 from day to day, are, no doubt, violent and 

 rapid beyond our utmost means of meas- 

 urement or expression. We say to-day's 

 sun is the same as yesterday's when we are 

 interested in the dawn and the daylight, 

 and in the flight of timei, and in the 

 change of seasons, and in the transit of 

 Veniis, and in the stability of the solar 

 system ; but we say it is not the same Avhen 

 we are interested in sun-spots, and in the 

 fall of meteorites, and in combustion and 

 the dissipation of energy. When we say 

 the solar system is stable, we do not mean 

 that it is really stable. We only mean that 

 the course of its progress from some past 

 condition to some future condition has no 

 obvious practical relation to our own affairs. 



We seldom lose sight of the diversity, 

 or individuality, of familiar living things 

 in our interest in their resemblances. We 

 do not say one horse is the same as another 

 between the shafts. We say he is as good 

 as another, or will serve, or that he is the 

 same substantially, meaning, by these 

 words, the sam,e substantially, or the same 

 in substance, that, while he is not the same, 

 we will accept him as a substitute ; but no 

 one with worldly wisdom trusts the strange 

 horse, even so far, before he has tested his 

 opinions, and those of the horse dealer, by 

 scientific experiment and verification. 



Biological science has peculiar fitness 

 for guarding us from the fallacy of the 

 undistributed middle, and for teaching us 

 that it is only through verification that 

 guesses become knowledge, because its sub- 

 ject matter lies midway between those 

 ' exact ' sciences in which we are told that 

 figures cannot lie, on the one hand, and, on 

 the other, those social and political sci- 

 ences which show us continually how easily 

 one may lie with figures. When we have 

 verified a hypothesis so often that we are 

 ' satisfied, ' we call it a ' laAv of nature, ' 

 and we build as firmly upon it, and trust to 

 it as implicitly, and govern our actions 

 by it as unhesitatingly, as if it were cer- 

 tain, and in all that concerns our conduct 

 we make little or no difference between it 

 and certain knowledge. In this, experi- 

 ence is continually demonstrating our Avis- 

 dom, but if the discovery that hypotheses 

 have no independent existence leads us to 

 believe that we can never know the real 

 world of nature, is it not time to reexam- 

 ine our notions? 



The laws of nature are real, but their 

 reality is not independent nor absolute, 

 because the unity of nature is unity in 

 diversity, and diversity in unity. 



If the views that are here advanced — 

 views that are in no way original with me 

 — are accepted; if the reality of the nat- 



