254 THE PRINCIPLES OF SCIENCE. 



is seen moving in the sky, or its constituent particles 

 illumine the heavens with their tails of fire. We cannot 

 explain the present movements of such a body without 

 supposing its prior existence, with a determinate amount 

 of energy and direction of motion ; nor can we validly 

 suppose that our task is concluded when we find that it 

 came wandering to our solar system through the un- 

 measured vastness of surrounding space. Every event 

 must have a cause, and that cause again a cause, until 

 we are lost in the obscurity of the past, and are driven 

 to the belief in one First Cause, by whom the whole 

 course of nature was determined. 



Fallacious Use of the Term Cause. 



The words Cause and Causation have given rise to in- 

 finite trouble and obscurity, and have in no slight degree 

 retarded the progress of science. From the time of 

 Aristotle, the work of philosophy has been often de- 

 scribed as the discovery of the causes of things, and 

 Francis Bacon adopted the notion when he said a ' vere 

 scire esse per causas scire.' Even now it is not uncom- 

 monly supposed that the knowledge of causes is some- 

 thing different from other knowledge, and consists, as it 

 were, in getting possession of the keys of nature. A 

 single word may thus act as a spell, and throw the 

 clearest intellect into confusion, as I have often thought 

 that Locke was thrown into confusion when endeavouring 

 to find a meaning for the word power.^ In Mr. Mill's 

 ' System of Logic ' the term cause seems to have re- 

 asserted its old noxious power. Not only does Mr. Mill 

 treat the Laws of Causation as almost co-extensive with 



a ' Novum Organum,' bk. ii. Aphorism 2. 



b ' Essay on the Human Understanding,' bk. ii. chap. xxi. 



