>According to legend, the door to Plato's Academy bore

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>According to legend, the door to Plato's Academy bore a phrase: "Let no man ignorant of geometry enter here."

>But as Plato himself clearly knew, because he wrote the Meno, his teacher Socrates demonstrated that all men understand geometry regardless of their training, by walking a slave who had never done any geometry as-such through a proof, and getting the slave's assent to the truth of the geometric statements made, thus re-discovering a piece of knowledge which the slave already knew