Aletheia (ἀλήθεια) — The Greek word for truth, read etymologically as “unconcealment” or “un-hiddenness”: the privative prefix a- (not) joined to the root of lēthē (concealment, forgetting), the same root as the mythical river Lethe of the waters of oblivion. On this reading, truth is not primarily a property of correct judgments but the very coming-to-light of what had been hidden. Among the Greeks the term already appears in pre-Socratic poetry, as in Parmenides, and Plato uses it for knowledge of the eternal Ideas, as opposed to mere opinion (doxa) and sensible appearance. The concept becomes central in the twentieth century with Martin Heidegger, who, in Being and Time (1927) and later writings, recovers the Greek sense of aletheia as the unconcealing of beings, the openness in which things show themselves as they are. To this disclosure there always belongs, essentially, a concealing: every manifestation carries with it what remains hidden or withdrawn. Heidegger contrasts this original truth with the conception that dominates the tradition — truth as adaequatio, that is, as the correspondence or adequation of a proposition to the fact it refers to. For him, such correspondence is possible only because beings have already been unconcealed beforehand. Aletheia is thus bound up with notions such as physis (the self-showing arising of nature) and with Heidegger’s critique of the forgetting of being, making it one of the key concepts of hermeneutic phenomenology.
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