We may indeed easily say outwardly with the lips that we doubt of all these things, because it is possible for us to lie ; but we cannot say this in our hearts. Thus Pyrrhonism is not a sect composed of men who are persuaded of what they say, but a sect of liars. Hence they often contradict themselves in uttering their opinion, since it is impossible for their hearts to agree with their language. We see this in Montaigne, who attempted to revive this sect in the last century ; for, after having said that the Academics were different from the Pyrrhonists, inasmuch as the Academics maintained that some things were more probable than others, which the Pyrrhonists would not allow, he declares himself on the side of the Pyrrhonists in the following terms : “The opinion,” says he, “of the Pyrrhonists is bolder, and much more probable.” There are, therefore, some things which are more probable than others. Nor was it for the sake of effect that he spoke thus : these are words which escaped him without thinking of them, springing from the depths of nature, which no illusion of opinions can destroy.
Antoine Arnauld, Pierre Nicole, The Port-Royal Logic, 1662, translated by Thomas Spencer Baines, 1861.
I love the last sentence here: “And don't you try to get out of it by claiming a sense of humor, either.” To me it hardly seems probable that Montaigne was not just saying that for effect. It's too perfect.