Lakatos' great friend and mentor at Debrecen University was Arpad Szabo, whose work I discovered through Lakatos. Szabo argued in The Beginnings of Greek Mathematics that the method of indirect proof, what we today call proof by contradiction, originated in poets including Parmenides and his logical analysis of "the One." In this paper I combine Szabo's ideas with those of Eric Havelock, who argued that the invention of the Greek alphabet and the transformation of Greek culture from orality to literacy provided the basis for much of Plato's philosophy. My goal was to show how the modern (Greek) conception of mathematical proof depends essentially on a literate culture.