224 THE PRINCIPLES OF SCIENCE. [CHAP. 



were equal to what they are at present, or they were 

 not ; if equal, we may make the same inquiry concerning 

 any other moment, however long prior, and we are thus 

 obliged to accept one horn of the dilemma existence 

 from infinity, or creation at some moment. This is but 

 one of the many cases^in which we are compelled to believe 

 in one or other of two alternatives, both inconceivable. 

 My present purpose, however, is to point out that we must 

 not confuse this supremely difficult question with that 

 into which inductive science inquires on the foundation of 

 facts. By induction we gain no certain knowledge ; but 

 by observation, and the inverse use of deductive reasoning, 

 we estimate the probability that an event which has 

 occurred was preceded by conditions of specified character, 

 or that such conditions will be followed by the event. 



Definition of the Term Cause. 



Clear definitions of the word cause have been given by 

 several philosophers. Hobbes has said, " A cause is the 

 sum or aggregate of all such accidents, both in the agents 

 and the patients, as concur in the producing of the effect 

 propounded ; all which existing together, it cannot be 

 understood but that the effect existeth with them ; or 

 that it can possibly exist, if any of them be absent." 

 Brown, in his Essay on Causation, gave a nearly corre- 

 sponding statement. "A cause," he says, 1 "may be 

 defined to be the object or event which immediately 

 precedes any change, and which existing again in similar 

 circumstances will be always immediately followed by a 

 similar change." Of the kindred word power, he like- 

 wise says : 2 " Power is nothing more than that invariable- 

 ness of antecedence which is implied in the belief of 

 causation." 



These definitions may be accepted with the qualifica- 

 tion that our knowledge of causes in such a sense can be 

 probable only. The work of science consists in ascertaining 

 the combinations in which phenomena present themselves. 



1 Observations on the Nature and Tendency of the Doctrine of 

 tfr. Hume, concerning the Relation of Cause and Effect. Second ed. 

 P. 44- 2 Ibid. p. 97. 



