For Heidegger, the interrelatedness of “non-being,” “being,” “sameness,” and “difference” begins at a point of misinterpretation/misunderstanding about the meaning of the question of Being. In other words, certain interpretations/understandings about the meaning of Being as a “question” that are not fulfilled with the interrelatedness of “non-being,” “being,” “sameness,” and “difference,” but rather, makes the meaning of Being a “question” that is further obscure, when Being is something that is taken for granted. Heidegger notes this in the reference to Sophist in Being and Time, pointing out the extent to which Being is forgotten. But, this reference is not so much an indictment of Parmenides—since, for Heidegger, in his Parmenides lecture, Parmenides is a primordial thinker thinking an authentic kind of thought—but is a criticism of Plato in particular. To be sure, Heidegger seems to suggest that Plato only uses “the stranger”—whether or not he is Parmenides notwithstanding—in a way that is ultimately disingenuous to Parmenidean thought, using it as a platform to think a thought that is inauthentic thinking about the meaning of the question of Being. It is safe to say, then, that Heidegger may see “the stranger” more as a mouthpiece for Plato’s thinking about Being (i.e. as what has been argued about Socrates’ role in the dialogues), and not a fair representation of Parmenides. More importantly, it may be fair to propose that this, at least in part, is a grounding component of Heidegger’s approach to Plato, and Heidegger’s assertion that Plato has not “concretely” worked out the meaning of the question of Being—no more than Plato has “concretely” worked the meaning of the question of sophistry in Sophist.
Finally, this brings me to Heidegger’s Plato’s Sophist, a lecture course given in the winter semester of 1924-1925 at Marburg, just before the publication of Being and Time, and his leaving for Freiburg to assume Husserl’s Philosophy Chair. It would seem, of course, that Heidegger would begin Plato’s Sophist in much the same manner as Being and Time: highlighting what Plato missed about the meaning of the question of Being. Heidegger, instead, suggests that the theme of the Being of beings must be accessed by way of “knowledge” and “aletheia.” Not only does this critique Sophist and its explanation of “being” and “non-being,” but Heidegger positions both as not in opposition, but in conjunction with one another, predicated on “aletheia” and Dasein—this, again, suggests that Plato does not understand the meaning of the question of Being as that which is relegated/regulated by “aletheia” and Dasein, and not by negation, sameness, and difference (as offered from the mouth of “the stranger”). This significance of “aletheia” and Dasein is not directly addressed with respect to Sophist, but is accessed “as a point of departure” with Aristotle and his Nicomachean Ethics and Metaphysics. It is not so much a “departure” as much as it is a way into Plato’s understanding of Being, in effect, qua Aristotle—that is to say, through Aristotle, as Heidegger seemingly suggests, the roles of ethics and knowledge intersect and convolute the authenticity of understanding the meaning of the question of Being, to the extent that certain ethics and knowledge place Being in concealment (“lethe”).
For Heidegger’s “Introductory Part,” by way of Aristotle, we can better articulate the meaning of Being through the meaning of “aletheuein”—it has five modes to it: “logos echon,” “episteme,” “techne,” “phronesis,” and “sophia,” with “aletheuein” as the ground of research into Being. Thereafter, in what announces itself as “The Main Part,” Heidegger presents some introductory remarks about Sophist (in much the same manner as I have done at the opening of this paper), proceeding carefully in a straightforward line-by-line exegesis up to Line 236c. After this point, at Line 236e, Heidegger denotes the introduction of an ontological discussion about “the Being of non-being,” or “pseudos logos” as an ontological problematic. The “problematic,” here, is with the contradictoriness of “pseudos logos”—in this, Heidegger identifies difficulties in the individual concepts of being and non-being, with special attention given to ancient and contemporary doctrines about “on,” both of which play significant roles in Sophist. That is to say, the difficulties in the “meaning” of being and the “meaning” of non-being rests in the “meaning” of Platonic ontology that simply does not reckon with—or even wrestle with—Being concretely, with “on.” In both cases, Heidegger differentiates the use of “on,” in order to set up a summary of the theses about “on,” with respect to the phenomenon of knowledge. What this means, I would argue, is that Heidegger believes that Plato’s ontology in Sophist—centered on “being” and “non-being”—is not an authentic ontology without working out the meaning of Being through the meaning of aletheuein, as the ground of research into Being. Plato’s “research into Being,” being sure to qualify it with quotes as a means of highlighting its inauthenticity—does not engage in a thinking that thinks the kind of thought necessary to disclose the meaning of Being in its Dasein-most-ness, in reference to the meaning of aletheuein.