Maria del Carmen Paredes interprets Plato and Heidegger's approaches to truth.
In our view, the Platonic theory of truth in Republic book 7 not only offers a certain conception of truth but contains as well a cluster of presuppositions giving support to the connection between being, truth, and good. Among these presuppositions is the awareness of the limits in gaining access to truth and the correlative need to hypotheses. Plato made clear in the image of the Line that the intelligible realm, which is the realm of knowledge, starts with hypotheses, some of which can be “destroyed” or “confirmed” as knowledge advances (R., 510b—11e, 533b—d). The concept of hypothesis is linked to the purpose of giving a positive answer to the problem of the beginning, or the "real" philosophical problem, as Hegel said. In Plato, the fundamental hypothesis is the initial presupposition of the Idea, which could eventually lead to genuine knowledge, that is, noesis. Thus, speaking about Ideas entails confirmation of some hypotheses, but only by way of analogy.
Heidegger’s approach is different from Plato’s. He seems to leave aside the implicit skepticism involved in the need for posing hypotheses and opts instead for something like a metaphysical approach when he offers the following metanarrative: "Truth no longer is, as unhiddenness, the basic feature of being itself, but it is, in consequence of having become correctness by bring yoked under the Idea, from this time forth the label for recognizing of beings . . . Herein lies an example of the interrelation between philosophical discourse and rhetoric in Heidegger’s essay on Plato. The hypothesis of the highest Idea enables Plato to give meaning to the existence of an ultimate source of truth, which can be no more than Good, and in a sense to traverse the road toward it. Certainly, Plato does not explain what he has in mind in writing that “it is Good which gives the things we know their truth and makes it possible for people to have knowledge” (R., 508elf.) either within the allegory of the cave or elsewhere in the Republic. On the contrary. he proposes rather that we forget about trying to define Good itself for the time being” (R., 506d8f.). It follows that the question remains unanswered or at least not explicitly answered in Plato’s dialogue. Heidegger’s main concern seems to be, by contrast, the thinking of Good within the frame of a fundamental ontology, hence Good not as a value or as an Idea.
For Heidegger, Good cannot be a value inasmuch as that would fall within the anthropological interpretations he rejects. But, then, Good can also not function as what gives value or validity to things. For pragmatism is not a possible solution to anthropocentrism to the extent that both belong to the same context of interpretation. In Plato, nevertheless, Good only functions as a possible ethical model because it is above all an ontological model. It stands as model for the universe or cosmos, so it can also function within the moral and political life of men. Ontologically considered, Good is the cause and source of truth and of the enduring reality of Forms. In other words, the solutions to the problem of morality and to the problem of knowledge go together. Wisdom does not consist only in knowing what it is but in acting in accordance with the ultimate validity of the order which encompasses man, the community and the cosmos. Heidegger’s analysis seems to follow a different path when he points to the problem of how an ontological conception of truth related to an axiological interpretation of the Good can supposedly open the road to the conformity between objects which possess the property of being good and the mind that determines or discovers it.