This book examines what we can reliably know about Plato and the historical Socrates. It shows how pervasively the sources of information were biased by Pythagoreanism, Platonism, and Neoplatonism. It gives a source-critical account of how the climate of opinion in fourth-century Athens was captured by the Pythagoreans and how Speusippos's Academy also came to be pythagorized--adding definitional idealism to Pythagorean number idealism, and elevating Plato to a divine level that makes him into a coequal of Pythagoras, thus capturing Plato for Pythagoreanism. By showing how Plato's dialogues were dedramatized, dedialogized, and read or understood as if they were works expounding pythagorizing doctrine, Tejera has created a provocative reappraisal for scholars of ancient Greek philosophy.