“Nor is he the wisest man who never proved himself a fool.”
Stanza 124
Locksley Hall Sixty Years After (1886)
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Alfred, Lord Tennyson 213
British poet laureate 1809–1892Related quotes

"Bobok : From Somebody's Diary" https://ebooks.adelaide.edu.au/d/dostoyevsky/d72bo/ as translated by Constance Garnett in Short Stories (1900) http://www.gutenberg.org/files/40745/40745-h/40745-h.htm
Context: A great many people were put down as mad among us last year. And in such language! "With such original talent"... "and yet, after all, it appears"... "however, one ought to have foreseen it long ago." That is rather artful; so that from the point of view of pure art one may really commend it. Well, but after all, these so-called madmen have turned out cleverer than ever. So it seems the critics can call them mad, but they cannot produce any one better.
The wisest of all, in my opinion, is he who can, if only once a month, call himself a fool — a faculty unheard of nowadays. In old days, once a year at any rate a fool would recognise that he was a fool, but nowadays not a bit of it. And they have so muddled things up that there is no telling a fool from a wise man. They have done that on purpose.
I remember a witty Spaniard saying when, two hundred and fifty years ago, the French built their first madhouses: "They have shut up all their fools in a house apart, to make sure that they are wise men themselves." Just so: you don't show your own wisdom by shutting some one else in a madhouse. "K. has gone out of his mind, means that we are sane now." No, it doesn't mean that yet.

Source: Epigrams, p. 345
“The weakest spot in every man is where he thinks himself to be the wisest.”
Source: Dictionary of Burning Words of Brilliant Writers (1895), P. 532.

“A man never knows what a fool he is until he hears himself imitated by one.”
Quoted by Max Beerbohm in Hebert Beerbohm Tree: Some Memories of Him and of His Art Collected by Max Beerbohm http://books.google.com/books?id=wM08AAAAIAAJ&q="A+man+never+knows+what+a+fool+he+is+until+he+hears+himself+imitated+by+one"&pg=PA312#v=onepage (1920).

“The wisest man is he who is certain he is not.”
Le plus sage est celui qui ne pense point l'être.
Satire 4
Satires (1716)

“And he is oft the wisest man
Who is not wise at all.”
The Oak and the Broom.
Bartlett's Familiar Quotations, 10th ed. (1919)

This Business of Living (1935-1950)

“The fool doth think he is wise, but the wise man knows himself to be a fool.”
Touchstone, Act V, scene i
Source: As You Like It (1599–1600)

“The fool doth think he is wise, but the wise man knows himself to be a fool.”
Touchstone, Act V, scene i
Misattributed