This text 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 4th-century Athens was captured by the Pythagoreans and how Speusippo'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.