As to temper and conceit and impudence and brass and lying, he was not half so bad twelve months ago as he is now. That is where I should have liked him to profit by your teaching; and we could have done, without his knowing the stuff he reels of at table every day: 'a crocodile seized hold of a baby,' says he, 'and promised to give it back if its father could answer'--the Lord knows what; or how, 'day being, night cannot be'; and sometimes his worship twists round what we say somehow or other, till there we are with horns on our heads!
Lucian of Samosata, Hermotimus. In this passage (supposedly a father complaining to a teacher), we see Lucian skewering the Stoic notion of good philosophy, suggesting that it neglects ethical behavior and amounts to nothing more than tiresome logic-chopping, resulting in students are worse than they were before they began to study. This is not really a new charge (cf. Aristophanes's mockery of the Socratics in The Clouds.) The problems identified here, however, are not caricatures: they were really discussed.
(1) The Crocodile Paradox. A crocodile seizes a baby on the banks of a river, but being a sophist says to the mother, "If you can accurately predict what I will do, I will return the child without eating it, but if you guess wrong, I will keep and eat it." To this, the mother replies, "You will keep and eat it." The crocodile says, "Aha! I cannot give the child back, because if I do, you will have predicted falsely. But if you predict falsely, I keep and eat it." "Ah," said the mother. "But you cannot keep and eat my baby, because if you do, I will have accurately predicted what you will do, and therefore you must return the child without eating it."
(2) Day and Night. The Greek is ambiguous between "Since it is day, it cannot be night" and "If day exists, night cannot exist."
(3) Horns. If you haven't lost a thing, you have it. You haven't lost your horns, have you? So you have them.
The complaint, then, boils down to the complaint that people who go to study philosophy end up really learning just how to twist words and arguments. Socrates had complained of the Sophists that they studied rhetoric not because it made them better, but because it gave them power -- the power to bully others. But the study of philosophy, Lucian suggests in the person of the exasperated father, is liable to the same abuse:
[A]nd if his mother asks him why he talks such stuff, he laughs at her and says if once he gets the 'stuff' pat off, there will be nothing to prevent him from being the only rich man, the only king, and counting every one else slaves and offscourings.
One could, I imagine, provide an updated version of the complaint here. "It would be wonderful if my child actually learned from you how to be a wiser person. But what we get when he sits down to talk with us is just a long list of bizarre science fiction and fairy tales, about splitting people, about rooms that speak Chinese, about places that have water that's not water and you's that aren't you, about people who know everything about colors that they've never seen, and Lord knows what; and if we argue anything, he always twists our argument, and if we say anything, he always squints at us and tells us we need to define our terms because he doesn't understand what we mean. And if we tell him he's talking nonsense, he talks airily of how we lack critical thinking skills, or fail to understand the value of being skeptical of assumptions, or are simply being irrational." And one wonders what the response would be that would be fundamentally different from the rather unimpressive one Lucian has the old teacher say.