396 MENTAL FUNCTIONS OF 



servation, he has only to study the heads of some celebrated men 

 now living, or the authentic casts of the departed, of whose talent? 



against him, and has always force enough to defend and establish it. History 

 shows us that all the efforts and sophisms which are directed against a truth once 

 drawn from darkness, fall like dust blown by the winds against a rock. 



" The instance of Aristotle and Descartes should be particularly quoted, when 

 we wish to display the influence of prejudice upon the good or bad fortune of 

 new doctrines. The opponents of Aristotle burnt his books ; afterwards, the 

 books of Ramus, who had written against Aristotle, were burnt, and the oppo- 

 nents of the philosopher of Stagira declared heretics ; and it was even forbidden 

 by law to dispute his doctrines, under pain of being sent to the galleys. Now 

 there is no longer any discussion about the philosophy of Aristotle. Descartes 

 was persecuted because he taught the innateness of ideas, and the University of 

 Paris burnt his books. He had written the most sublime thoughts upon the 

 existence of God; Voe't, his enemy, accused him of atheism. Afterwards, this 

 same university declares itself in favour of innate ideas; and when Locke and 

 Condillac attacked innate ideas, the cry of materialism and fatalism resounded 

 on all sides. 



" Thus, the same opinions have at one time been regarded as dangerous because 

 they were new, and at another as useful because they were ancient. We must, 

 therefore, pity mankind, and conclude that the opinions of contemporaries as to 

 the truth or error, and dangerous or innocent tendencies, of a doctrine, are very 

 suspicious, and that the author of a discovery should be anxious only to ascertain 

 whether he has really discovered a truth or not. A truth once discovered, will 

 make its way, and not fail to produce good effects. * Reason,' says Ancillon, 

 after Bonnet, 'knows no useless nor dangerous truths. What is, is.' This is 

 indisputable, and is the only answer to be made to those who, putting all things 

 in subordination to men's wants, ask, What is the use of that ? and, to those who, 

 always yielding to fear, ask, What may that lead to ? Jesus, the son of Sirach, 

 had already said, ' we ought not to ask what is the use of that : for the use will 

 have its reward in time.' " * 



When delivering the Lumleyan lectures, and asserting the importance of per- 

 cussion and auscultation, for the first time, before the College of Physicians, in 

 1829, I reminded the College, "that the greatest discoveries had generally been 

 at first ridiculed, and their authors, no less than all the truest benefactors of the 

 human race, despised and rejected of men. 



' Romulus, et Liber Pater, et cum Castore Pollux ; 



Dum terras hominumque colunt genus, aspera bella 



Componunt, agros assignant, oppida condunt, 



Ploravere suis non respondere favorem, 



Speratum mentis.'" Hon. Ep. 1. lib. ii. 



* 1. c. 8vo. t. i. p. 221. sqq., 4to. t. iv. p. 75. sqq., where alone the sentence 

 " a truth once discovered," is found ; but where the third and fourth paragraphs 

 are not. 



