THE UNIFORMITY OF NATURE. 251 



versally, and that therefore the unexplained errors of Uranus were 

 due to the action of an exterior planet. But this assumption was as 

 different as possible from a postulate : it was only applying in a new 

 way a law which had already been verified in so many and such diverse 

 cases that there was scarcely the shadow of a doubt in the mind of 

 any astronomer that it was, as its ordinary name professes it to be, 

 universal throughout the material cosmos. 



I am confirmed in this belief by finding the subsequent statement 

 that " the uniformity of Nature is a working hypothesis, and it never 

 can be more " ; * which agrees very much with the view propounded 

 by Professor Huxley at the meeting of the Metaphysical Society. But 

 I am not quite sure that this is consistent with a previous passage in 

 the lecture, which runs thus : 



This, then, is the answer to the question. Why do we believe in the uniform- 

 ity of Nature ? We believe in it because we find it so. Millions and millions of 

 observations concur in exhibiting this uniformity. And, the longer our observa- 

 tion of Nature goes on, tlie greater do we find the extent of it. Things which 

 once seemed irregular are now known to be regular. Things that seemed inex- 

 plicable on this hypothesis are now explained. Every day seems to add not 

 merely to the instances, but to the wide-ranging classes of phenomena that come 

 under the rule.t 



The truth of which I am not concerned to dispute ; but the para- 

 graph gives a very different complexion to the principle of the uni- 

 formity of Nature from that which belongs to it, when regarded as a 

 postulate upon which all scientific knowledge depends. 



The truth which I think is postulated in the case of Nature is that 

 which is involved in the idea of cause and effect. The Bishop of Lon- 

 don refers to Hume's famous discussion of this question, and his con- 

 clusion that there is nothing more in cause and effect than the notion 

 of invariable sequence. This conclusion has often been controverted, 

 and the Bishop of London refers to the arguments of Kant and of J. 

 S. Mill : it seems to admit of a very simple and irresistible contradic- 

 tion from the following consideration : It is easy to give instances in 

 which an invariable sequence takes place, and yet the two events which 

 follow each other are obviously not connected as cause and effect. 

 Take the case of lightning and thunder : the thunder follows the light- 

 ning with invariable sequence, whether we chance to hear it or not, 

 but the two are separate effects of the same cause acting under differ- 

 ent conditions ; and no rightly instructed person could imagine that 

 one was the effect of the other. Or suppose that you shout, and pro- 

 duce two echoes from two rocks at different distances ; these echoes 

 will satisfy the condition of invariable sequence, and yet will mani- 

 festly not be related as cause and effect. Or, to put the case more 

 generally, it is quite possible that a cause may produce more than one 



* Page 29. f Page 27. 



