Martin Heidegger’s analysis of Platos’ Theaetetus can be found in The Essence of Truth (Continuum, 2002). The Theaetetus is constructed in the form of a dialogue, between Socrates and Theaetetus, and discusses the nature of knowledge. Heidegger, whose analysis covers only the central section of the conversation, understands knowledge as a form of truth.
As his book’s title suggests, Heidegger’s intention is to address the theme of truth, in particular the Greek idea of truth as aletheia, which means unhiddenness, in contrast to our understanding of truth as correctness, given by the Latin term veritas. The Essence of Truth is part of Heidegger’s project to bring into the open what he believes we have long forgotten, that is being, that which is present in addition to what is physically there.
“An understanding of Being is already included in conceiving anything which one apprehends as an entity.”Thomas Aquinas, Summa Theologica
Aletheia, is the experience of the unhiddeness of being, what something shows itself as. Heidegger proposes that this return to being as aletheia be re-enacted by examining the essence of truth, by asking “what is truth?” In order to do this aletheia itself must be put into question by exploring what beings are prior to unconcealment, i.e. as hidden, as untruth – pseudos, the false. Therefore the title of Heidegger ‘s analysis, in the second part of The Essence of Truth: “an interpretation of Plato’s Theaetetus with respect to the question of the essence of untruth.”