With Plato  , this early Greek conception of φύσις-ἀλήθεια [physis-aletheia], sc. truth conceived as non-concealment [Unverborgenheit], undergoes a transformation, for, although on the one hand the Ideas retain the original sense of ἀ-λήθεια [a-letheia], insofar as they are conceived fundamentally as a source of light [Licht] by reason of which, through participation [methexis], the “beings” of experience shine forth, nevertheless the Ideas become at the same time something-to-be-seen (εἶδος:ἰδεῖν), and truth [Wahrheit] comes gradually to mean the proper viewing of the Ideas, the conformity (ὀρθότης [orthotes]) between the being that views and the Ideas (conceived as beings) that are viewed. Here the Ideas are transformed from a source of light into that-which-is-viewed. In other words, Being [Sein] is reduced to a being [Seiende]. The confusion will mark the entire subsequent history of metaphysics [Metaphysik]. Token of the confusion will be the domination henceforth of the conception of truth as conformity and a disregard of the original sense of truth as non-concealment. Since truth-as-non-concealment is what Heidegger understands by Being, it is easy to see in what sense he understands metaphysics as the perennial forgetfulness of Being [Seinsvergessenheit]. [RHPT:17]