258 THE PRINCIPLES OF SCIENCE. 



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/ 

 Dr. Brown, in his * Essay on Causation/ gave a nearly 

 corresponding statement. *A cause,' he says e , 'may be 

 denned 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 : f ' 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 ascer- 

 V taining the combinations in which phenomena present 

 themselves.. Concerning every event we shall have to 

 determine its probable conditions, or group of antecedents 

 from which it probably follows. An antecedent is any- 

 thing which exists prior to an event ; a consequent is 

 anything which exists subsequently to an antecedent. It 

 will not usually happen that there is any probable con- 

 nection between an antecedent and consequent. Thus 

 nitrogen is an antecedent to the lighting of a common 

 \ fire ; but it is so far from being a cause of the lighting, 

 that it renders the combustion less active. Daylight is 

 an antecedent to all fires lighted during the day, but it 

 probably has no appreciable effect one way or the other. 

 But in the case of any given event it is usually pos- 

 sible to discover a certain number of antecedents which 



e ' Observations on the Nature and Tendency of the Doctrine of 

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

 p. 44. f Ibid. p. 97. 



