C.S. Lewis, from his 1944 Memorial Lecture at King’s College, University of London:

It would be polite and charitable, and in view of your age reasonable too, to suppose that none of you is yet a scoundrel. On the other hand, by the mere law of averages (I am saying nothing against free will) it is almost certain that at least two or three of you before you die will have become something very like scoundrels. There must be in this room the makings of at least that number of unscrupulous, treacherous, ruthless egotists. The choice is still before you: and I hope you will not take my hard words about your possible future characters as a token of disrespect to your present characters.

And the prophecy I make is this. To nine out of ten of you the choice which could lead to scoundrelism will come, when it does come, in no very dramatic colours. Obviously bad men, obviously threatening or bribing, will almost certainly not appear. Over a drink, or a cup of coffee, disguised as triviality and sandwiched between two jokes, from the lips of a man, or woman, whom you have recently been getting to know rather better and whom you hope to know better still—just at the moment when you are most anxious not to appear crude, or naïf or a prig—the hint will come. It will be the hint of something which the public, the ignorant, romantic public, would never understand: something which even the outsiders in your own profession are apt to make a fuss about: but something, says your new friend, which “we”—and at the word “we” you try not to blush for mere pleasure—something “we always do.”

And you will be drawn in, if you are drawn in, not by desire for gain or ease, but simply because at that moment, when the cup was so near your lips, you cannot bear to be thrust back again into the cold outer world. It would be so terrible to see the other man’s face—that genial, confidential, delightfully sophisticated face—turn suddenly cold and contemptuous, to know that you had been tried for the Inner Ring and rejected. And then, if you are drawn in, next week it will be something a little further from the rules, and next year something further still, but all in the jolliest, friendliest spirit. It may end in a crash, a scandal, and penal servitude; it may end in millions, a peerage and giving the prizes at your old school. But you will be a scoundrel.