“The surest way to corrupt a youth is to instruct him to hold in higher esteem those who think alike than those who think differently.”

Source: On Liberty (1859), Ch. II: Of the Liberty of Thought and Discussion

Source: Freedom from Fear (1991)
Context: It is not power that corrupts but fear. Fear of losing power corrupts those who wield it and fear of the scourge of power corrupts those who are subject to it. Most Burmese are familiar with the four a-gati, the four kinds of corruption. Chanda-gati, corruption induced by desire, is deviation from the right path in pursuit of bribes or for the sake of those one loves. Dosa-gati is taking the wrong path to spite those against whom one bears ill will, and moga-gati is aberration due to ignorance. But perhaps the worst of the four is bhaya-gati, for not only does bhaya, fear, stifle and slowly destroy all sense of right and wrong, it so often lies at the root of the other three kinds of corruption. Just as chanda-gati, when not the result of sheer avarice, can be caused by fear of want or fear of losing the goodwill of those one loves, so fear of being surpassed, humiliated or injured in some way can provide the impetus for ill will. And it would be difficult to dispel ignorance unless there is freedom to pursue the truth unfettered by fear. With so close a relationship between fear and corruption it is little wonder that in any society where fear is rife corruption in all forms becomes deeply entrenched.

Letter to Anne, Countess of Ossory, (16 August 1776)
A favourite saying of Walpole's, it is repeated in other of his letters, and might be derived from a similar statement attributed to Jean de La Bruyère, though unsourced: "Life is a tragedy for those who feel, and a comedy for those who think". An earlier form occurs in another published letter:
I have often said, and oftener think, that this world is a comedy to those that think, a tragedy to those that feel — a solution of why Democritus laughed and Heraclitus wept.
Letter to Sir Horace Mann (31 December 1769)
Variant: The world is a comedy to those that think; a tragedy to those that feel.

Source: I Have Chosen to Stay and Fight

La vie est une tragédie pour celui qui sent, et une comédie pour celui qui pense.
As quoted in Selected Thoughts from the French: XV Century-XX Century, with English Translations (1913), pp. 132-133, by James Raymond Solly. This may conceivably be a misattribution, because as yet no definite citation of a specific work by La Bruyère has been located, and the statement is very similar to one known to have been made by Horace Walpole in a letter of 31 December 1769: The world is a comedy to those that think; a tragedy to those that feel.