GROWTH AND DECAY OF MIND. 333 



same author when he has made for himself a name, when he knows 

 something of the feeling of the public as to his powers, and when also 

 he has learned to distinguish the qualities he possesses — to see where 

 he is strong and where weak — will have an air of strength and firm- 

 ness not due, or only partially due, to any real growth of his mental 

 powers. But, as I have said, and as experience has repeatedly shown, 

 it is in opinions formed as to the diminution of mental power that the 

 world is most apt to be deceived. How commonly the remark is heard 

 that So-and-so has written himself out, or Such-a-one is not the man 

 he was, when in reality, as those know who are intimate with the author 

 so summarily dismissed, the deterioration, justly enough noted, is due 

 to circumstances in no way connected with mental capacity ! The 

 author who has succeeded in establishing a reputation may not have 

 (nay, very commonly has not) the same reason for exerting his powers 

 to the full, as he had when he was making his reputation. He may 

 have less leisure, more company, new sources of- distraction, and so on. 

 The earlier work, his chef-d'oeuvre, let us say, may have been produced 

 at one great effort, no other subject being allowed to occupy his at- 

 tention until the masterpiece had been completed — the later and in- 

 ferior work, hastily accepted as evidence that the author's mind no 

 longer preserves its wonted powers, may have been written hurriedly 

 and piecemeal, and subjected to no jealous revision before passing 

 through the press. 



Here I have taken literary w r ork as affording typical instances. But 

 similar misapprehensions are common in other departments of mental 

 work. For example, it is related that ISTewton, long before he was an 

 old man, said of himself that he could no longer follow the reasoning 

 of his own " Principia," and this has commonly been accepted as evi- 

 dence that his mind had lost power. The conclusion is an altogether 

 unsafe one, as every mathematician knows. It w r ould have been a 

 truly wonderful circumstance if Newton had been able, even only ten 

 or twelve years after his magnum opus was completed, to follow its 

 reasoning with satisfaction to his own mind — that is, with the feeling 

 that he still had that grasp of the subject which he had possessed 

 when, after long concentration of his thoughts upon it, he was engaged 

 in the task of exhibiting a summary of his reasoning (for the " Prin- 

 cipia " is scarcely more). 



I can give more than one instance, in my own experience, of this 

 seeming loss of mastery over a mathematical subject, while in reality 

 the mind has certainly not deteriorated in its power of dealing with 

 subjects of that particular kind. I will content myself with one. It 

 happened that in 1869 I had occasion to examine a mathematical sub- 

 ject of no very great difficulty, but involving many associated rela- 

 tions, and requiring therefore a considerable amount of close attention. 

 At that time I had made myself master, I think I may say without 

 conceit, of that particular subject in all its details. Recently, I had 



