192 MEMOIR OF AUGUSTUS DE MORGAN. 



to whose experience this and all its kindred manifestations 

 were so completely opposed, sought for explanation in the 

 credulity and inability to observe of the believers. Mr. 

 Faraday combated the influx of superstition in a lecture 

 On Mental Training., given in the spring of 1854, at the 

 Royal Institution. In this lecture he affirmed a principle, 

 which Mr. De Morgan commented on two years after in a 

 review of the printed lecture in the AthenoBum. Will 

 the time ever come when the reviewer's caution will be 

 needless P 



The lecturer has laid down in the strongest and plainest 

 terms the principle of Physics, which was the bane of what is 

 known as the Philosophy of the Schoolmen. It occurs in a 

 lecture On Mental Training, delivered May 6, 1854, at the Royal 

 Institution. These are his own words : 



' The laws of nature as we understand them are the founda- 

 tions of our knowledge of natural things. Before we proceed to 

 consider any questions involving physical principles we should 

 set out with clear ideas of the naturally possible and impossible. 1 



We stared when we read this, ' set out in physical investiga- 

 tions with a clear idea of the naturally possible and impossible ' ' 

 We thought the world had struggled forward to the knowledge 

 that a clear idea of this was the last acquisition of study and 

 reflection combined with observation, not the possession of our 

 intellect at starting. We thought that mature minds were 

 rather inclined to believe that a knowledge of the limits of 

 possibility and impossibility was only the mirage which constantly 

 recedes as we approach it. We remembered the Platonic idea, as 

 clear as the crystalline orbs it led to, that the planetary motions 

 must be circular, or compounded of circular motion, and that 

 aught else was impossible. We remembered with how clear an 

 idea of the impossibility of the earth's motion the first opponents 

 of Galileo started these maxims into the dispute. We doubt if in 

 any mediaeval writer the principle on which they acted has been 

 so broadly laid down as by our author in the phrases above 

 quoted. The schoolmen did indeed make laws of nature the 

 foundation of their knowledge, and clear ideas of possibility and 

 impossibility helped them in the structure. But they rather did 

 it than professed it. Athenaeum, March 1855. 



Mr. Faraday believed that a full explanation of the 



