DEAR BOY: Those who suppose that men in general act rationally, because they are called rational creatures, know very little of the world, and if they act themselves upon that supposition, will nine times in ten find themselves grossly mistaken. That man is, 'animal bipes, implume, risibile', I entirely agree; but for the 'rationale', I can only allow it him 'in actu primo' (to talk logic) and seldom in 'actu secundo'. Thus, the speculative, cloistered pedant, in his solitary cell, forms systems of things as they should be, not as they are; and writes as decisively and absurdly upon war, politics, manners, and characters, as that pedant talked, who was so kind as to instruct Hannibal in the art of war. Such closet politicians never fail to assign the deepest motives for the most trifling actions; instead of often ascribing the greatest actions to the most trifling causes, in which they would be much seldomer mistaken. They read and write of kings, heroes, and statesmen, as never doing anything but upon the deepest principles of sound policy. But those who see and observe kings, heroes, and statesmen, discover that they have headaches, indigestions, humors, and passions, just like other people; everyone of which, in their turns, determine their wills, in defiance of their reason. Had we only read in the "Life of Alexander," that he burned Persepolis, it would doubtless have been accounted for from deep policy: we should have been told, that his new conquest could not have been secured without the destruction of that capital, which would have been the constant seat of cabals, conspiracies, and revolts. But, luckily, we are informed at the same time, that this hero, this demi-god, this son and heir of Jupiter Ammon, happened to get extremely drunk with his w---e; and, by way of frolic, destroyed one of the finest cities in the world. Read men, therefore, yourself, not in books but in nature. Adopt no systems, but study them yourself. Observe their weaknesses, their passions, their humors, of all which their understandings are, nine times in ten, the dupes. You will then know that they are to be gained, influenced, or led, much oftener by little things than by great ones; and, consequently, you will no longer think those things little, which tend to such great purposes.