“Each of us is sometimes a cretin, a fool, a moron, or a lunatic. A normal person is just a reasonable mix of these components, these four ideal types.”

“There are four kinds of people in this world: cretins, fools, morons, and lunatics…Cretins don’t even talk; they sort of slobber and stumble…Fools are in great demand, especially on social occasions. They embarrass everyone but provide material for conversation…Fools don’t claim that cats bark, but they talk about cats when everyone else is talking about dogs. They offend all the rules of conversation, and when they really offend, they’re magnificent…Morons never do the wrong thing. They get their reasoning wrong. Like the fellow who says that all dogs are pets and all dogs bark, and cats are pets, too, therefore cats bark…Morons will occasionally say something that’s right, but they say it for the wrong reason…A lunatic is easily recognized. He is a moron who doesn’t know the ropes. The moron proves his thesis; he has logic, however twisted it may be. The lunatic on the other hand, doesn’t concern himself at all with logic; he works by short circuits. For him, everything proves everything else. The lunatic is all idée fixe, and whatever he comes across confirms his lunacy. You can tell him by the liberties he takes with common sense, by his flashes of inspiration, and by the fact that sooner or later he brings up the Templars…There are lunatics who don’t bring up the Templars, but those who do are the most insidious. At first they seem normal, then all of a sudden…”

“A library's ideal function is to be a little bit like a bouquiniste's stall, a place for trouvailles.”

“The lunatic is all idée fixe, and whatever he comes across confirms his lunacy. You can tell him by the liberties he takes with common sense, by his flashes of inspiration, and by the fact that sooner or later he brings up the Templars.”

“And when someone suggests you believe in a proposition, you must first examine it to see whether it is acceptable, because our reason was created by God, and whatever pleases our reason can but please divine reason, of which, for that matter, we know only what we infer from the processes of our own reason by analogy and often by negation.”

“Whoever reflects on four things I would be better if he were never born: that which is above, that which is below, that which is before, that which is after.”

“For centuries, as pope and emperor tore each other apart in their quarrels over power, the excluded went on living on the fringe, like lepers, of whom true lepers are only the illustration ordained by God to make us understand this wondrous parable, so that in saying 'lepers' we would understand 'outcast, poor, simple, excluded, uprooted from the countryside, humiliated in the cities.' But we did not understand; the mystery of leprosy has continued to haunt us because we have not recognized the nature of the sign.”