THE SCOPE OF PHILOSOPHY 



Having thus, at the risk of tediousness, 

 shown in detail the essential identity of the 

 processes involved in science and in ordinary 

 knowledge, let us go on to enumerate the re- 

 spects in which science differs from ordinary- 

 knowledge, bearing in mind as we proceed that 

 such distinctions can only hold good to a cer- 

 tain extent. They are not differences of kind, 

 but differences of degree. 



In the first place we may say that science 

 differs from ordinary knowledge in its power 

 of quantitative prevision — of assigning before- 

 hand the precise amount of effect which will be 

 produced by a given amount of cause. Mere 

 prevision is not, as is sometimes assumed, pecu- 

 liar to science. We frequently hear it assigned, 

 as the distinguishing characteristic of scientific 

 knowledge, that it enables us to predict ; and 

 the infallibility of the predictions of science is 

 commonly alluded to as among its greatest 

 triumphs. Nevertheless, when the schoolboy 

 throws a stone into the air, he can predict its 

 fall as certainly as the astronomer can predict 

 the recurrence of an eclipse ; but his prevision, 

 though certain, is rude and indefinite. The 

 servant-girl has no need of chemistry to teach 

 her that, when the match is applied, the fire 

 will burn and smoke ascend the chimney ; but 

 she is far from being able to predict the pro- 

 portional weights of oxygen and carbon which 

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