... fools are insolent and their presumptions insult the mind. Thus we avenge intelligence when we refute a fool, and the victory is worth the trouble, for he is protected as with armor, and we do not know where to strike him. Refuting a fool, in short, is an endeavor worthy of a man of wit.-- Casanova, The Story of my Life (tr. Sartarelli & Hawkes), preface.
... I've substituted "refute" for "deceive," because as we know, Casanova was not chiefly interested in blogging. He makes a pleasant distinction between fools and those who are simply stupid: "I am rather fond of such men, who are stupid only for want of proper breeding. I have found some to be quite upright, in fact, and who in the nature of the stupidity had a kind of intelligence. They are like eyes that, if not for their cataracts, would be very beautiful."
Casanova is also our source for one of Voltaire's best qui vive one-liners; the adventurer told Voltaire he'd been to see one Haller, an inveterate opponent of Voltaire's.
Voltaire: "My compliments. One must kneel before that great man."
Casanova: "I agree. You do him justice; I regret, however, that he is not quite so equitable towards you."
Voltaire: "Ah, well! It is quite possible we are both mistaken."