Plato, Descartes, and Pragmatists?

Plato, Descartes, and the Pragmatists each caution about the limits of knowledge. Socrates says he is ignorant, Descartes says we must limit ourselves to affirming only what “the intellect clearly and distinctly discloses”, and the Pragmatists say that we cannot “know when we know the truth.” Outline, compare and contrast each of their positions and state your own.