From Montaigne et la philosophie by Marcel Conche:

Montaigne is ironic about the words of Protagoras: “Truly Protagoras was telling us some good ones, making man the measure of all things, who never even knew his own…. he being in himself so contradictory, and one judgment incessantly subverting another, that favorable proposition was just a joke which led us necessarily to conclude the nullity of the compass and the compasser.” How can man be the measure of all things? There is no such thing as man in the abstract, there are only men whose contrary judgments are mutually subversive. How can we talk, then, about a “standard man,” for measuring all others? There is neither standard measure nor absolute measurer… There is not, even, an immutable self, but only the scattering of multiple selves: “We are all patchwork, and so shapeless and diverse in composition that each bit, each moment, plays its own game. And there is as much difference between us and ourselves as between us and others.” There is no way of seeing the world that would be that of the “standard man,” nor that would be “mine,” for the moment is all-important…. things are seen, here and there, in different ways; if particular perspectives are taken as absolute “truth,” they destroy each other. So we must not do so. Values must be related to their sphere of validity, they must not be reified into dogmas, principles, truths, “objective” good or evil, all of which would claim to be universally valid.

Translation: Montaigne quotes by Donald Frame, the rest by me.