ch. ii.] THE SCOPE OF PHILOSOPHY. 33 



frequently hear it assigned, as tne distinguishing charac- 

 teristic 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 pre- 

 dict 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 proportional weights of oxygen 

 and carbon which will unite, the volume of the gases which 

 are to be given off, or the intensity of the radiation which is 

 to warm the room. Her prevision is qualitative, not quanti- 

 tative in its character : she can foresee the kind of effect, but 

 not its amount. 



A moment's reflection, however, will show us that this 

 statement, as it stands, does not convey the whole truth. It 

 is not quite true that our servant-girl can foresee the kind of 

 effect. She can foresee a part of it : she can tell us that the 

 wood will burn, but she will know nothing about the union 

 of oxygen with carbon ; and will thus illustrate the super- 

 iority of science even with respect to qualitative prevision. 

 On the other hand, she can, after a rude fashion, foresee the 

 amount of effect which will follow her proceedings ; since 

 she can, if intelligent, estimate the amount of fuel which 

 will be required to produce a comfortable warmth. So the 

 savage can estimate the amount of tension which he must 

 impart to his bow in order to send his arrow to the requisite 

 distance. Thus we see that, even with respect to quantitative 

 prevision, science can be distinguished from ordinary know- 

 ledge only by the superior accuracy and greater extent to 

 which it carries such prevision. Just this same difference of 

 degree between science and ordinary knowledge constitutes 

 also the chief difference between the more developed and the 



VOL. I. D 



