How did the Stoics respond to the Skeptics?

Epictetus does not treat the Skeptics as a rival school offering a reasonable alternative. He treats their central claim as self-defeating. When a Pyrrhonist says nothing can be known, or an Academic says no one should believe anybody, that person is using reason to argue you into a conclusion, which already assumes reason works and that you should be persuaded by good argument (Discourses II 20). Epictetus makes the same move against Epicurus, who denies natural fellowship among human beings while relying on you trusting his word not to be deceived (Discourses II 20). The pattern is the same: the position undoes itself the moment it is spoken.

The common misreading is that Stoicism dismissed the Skeptics by refusing to engage, as if certainty were simply asserted by fiat against doubt. That is not what happens in the text. Epictetus takes the challenge seriously enough to give an argument: some propositions are so evident that even denying them requires using them (Discourses II 20). If someone claims nothing is universally true, they have just made a universal claim. If someone tells you not to believe anyone, they are asking you to believe them. This is not stubbornness dressed up as philosophy. It is a demonstration that total suspension of judgment cannot actually be lived, because the Skeptic still walks toward food and away from cliffs, still forms opinions and acts on them.

At the same time, Epictetus admits the limits of argument itself. Some people, he says, have hardened themselves against evident truths, and no fire or iron will make a man feel what he refuses to feel (Discourses I 5). He compares this to a kind of living death: a person who perceives the contradiction in his own position but pretends not to, is worse off than someone who genuinely cannot understand (Discourses I 5). This matters because it shows the Stoic response is not just logical. It is also diagnostic. Some resistance to evident truth is an intellectual failure, and some is a moral one, a hardened unwillingness to feel shame at being wrong.

Epictetus's broader answer to Skepticism runs through his theory of assent. He holds that assent naturally inclines toward what appears true and withholds itself before what is uncertain, and that no one can simply choose to believe it is night when it plainly is day (Discourses I 28). This is his reply to the suggestion that we could or should suspend judgment about everything: assent is not free-floating. It tracks the evidence. Where the Academics and Pyrrhonists see grounds for universal suspension, Epictetus sees a faculty that has to be trained, not switched off. He calls this an art with respect to giving assent (Meditations 11.37), a discipline of judging correctly rather than refusing to judge at all.

What changes if you take this seriously is where you locate the target of philosophical training. The Stoic does not fight Skepticism by claiming certainty about everything. Externals remain uncertain, and much of life is contingent. But the faculty of assent itself, the fact that you are the kind of being who judges, cannot coherently be doubted away, since doubting is itself a judgment. Epictetus's own advice is to meet whatever unsettles you where it operates: if sophisms are what trouble you, apply the remedy of reason to sophisms directly (Discourses I 27), have your principles ready in advance rather than improvised in the moment.

The practical upshot is a habit, not a slogan. When you catch yourself in a stance of blanket doubt, ask what that stance requires you to already accept. Usually it requires trusting your own reasoning enough to have reached the doubt in the first place.