This extract from the IEP article on Heidegger is especially clarifying:
". . . The conception of the history of being is of central importance in Heidegger’s thought. Already in Being and Time its idea is foreshadowed as “the destruction of the history of ontology.” In Heidegger’s later writings the story is considerably recast and called the “history of being” (Seinsgeschichte). The beginning of this story, as told by Heidegger especially in the Nietzsche lectures, is the end, the completion of philosophy by its dissolution into particular sciences and nihilism—questionlessness of being, a dead end into which the West has run. Heidegger argues that the question of being would still provide a stimulus to the research of Plato and Aristotle, but it was precisely with them that the original experience of being of the early Greeks was covered over. The fateful event was followed by the gradual slipping away of the distinction between being and beings. Described variously by different philosophers, being was reduced to a being: to idea in Plato, substantia and actualitas in Medieval philosophy, objectivity in modern philosophy, and will to power in Nietzsche and contemporary thought. The task which the later Heidegger sets before himself is then to make a way back into the primordial beginning, so that the “dead end” can be replaced by a new beginning. And since the primordial beginning of western thought lies in ancient Greece, in order to solve the problems of contemporary philosophy and reverse the course of modern history, Heidegger ultimately turns for help to the Presocratics, the first western thinkers.
5. Overcoming Metaphysics
For the later Heidegger, “western philosophy,” in which there occurs forgetfulness of being, is synonymous with “the tradition of metaphysics.” Metaphysics inquires about the being of beings, but in such a way that the question of being as such is disregarded, and being itself is obliterated. The Heideggerian “history of being” can thus be seen as the history of metaphysics, which is the history of being’s oblivion. However, looked at from another angle, metaphysics is also the way of thinking that looks beyond beings toward their ground or basis. Each metaphysics aims at the fundamentum absolutum, the ground of such a metaphysics which presents itself indubitably. In Descartes, for example, the fundamentum absolutum is attained through the “Cogito” argument. Cartesian metaphysics is characterized by subjectivity because it has its ground in the self-certain subject. Furthermore, metaphysics is not merely the philosophy which asks the question of the being of beings.At the end of philosophy—i.e., in our present age where there occurs the dissolution of philosophy into particular sciences—the sciences still speak of the being of what-is as a whole. In the wider sense of this term, metaphysics is thus, for Heidegger, any discipline which, whether explicitly or not, provides an answer to the question of the being of beings and of their ground. In medieval times such a discipline was scholastic philosophy, which defined beings as entia creatum (created things) and provided them with their ground in ens perfectissimum (the perfect being), God. Today the discipline is modern technology, through which the contemporary human being establishes himself in the world by working on it in the various modes of making and shaping. Technology forms and controls the human position in today’s world. It masters and dominates beings in various ways.
“In distinction from mastering beings, the thinking of thinkers is the thinking of being.” Heidegger believes that early Greek thinking is not yet metaphysics. Presocratic thinkers ask the question concerning the being of beings, but in such a way that being itself is laid open. They experience the being of beings as the presencing (Anwesen) of what is present (Anwesende). Being as presencing means enduring in unconcealment, disclosing. Throughout his later works Heidegger uses several words in order rightly to convey this Greek experience. What-is, what is present, the unconcealed, is “what appears from out of itself, in appearing shows itself , and in this self-showing manifests.” It is the “emerging arising, the unfolding that lingers.” He describes this experience with the Greek words phusis (emerging dominance) and alêtheia (unconcealment).He attempts to show that the early Greeks did not “objectify” beings (they did not try to reduce them to an object for the thinking subject), but they let them be as they were, as self-showing rising into unconcealment. They experienced the phenomenality of what is present, its radiant self-showing. The departure of Western philosophical tradition from concern with what is present in presencing, from this unique experience that astonished the Greeks, has had profound theoretical and practical consequences.
According to Heidegger, the experience of what is present in presencing signifies the true, unmediated experience of “the things themselves” (die Sache selbst). We may recall that the call to “the things themselves” was included in the Husserlian program of phenomenology. By means of phenomenological description Husserl attempted to arrive at pure phenomena and to describe beings just as they were given independently of any presuppositions. For Heidegger, this attempt has, however, a serious drawback. Like the tradition of modern philosophy preceding him, Husserl stood at the ground of subjectivity. The transcendental subjectivity or consciousness was for him “the sole absolute being.” It was the presupposition that had not been accounted for in his program which aimed to be presuppositionless. Consequently, in Heidegger’s view, the Husserlian attempt to arrive at pure, unmediated phenomena fails. Husserl’s phenomenology departs from the original phenomenality of beings and represents them in terms of the thinking subject as their presupposed ground. By contrast, Heidegger argues, for the Presocratics, beings are grounded in being as presencing. Being, however, is not a ground. To the early Greeks, being, unlimited in its dis-closure, appears as an abyss, the source of thought and wonder. Being calls everything into question, casts the human being out of any habitual ground, and opens before him the mystery of existence.
The departure of western philosophical tradition from what is present in presencing results in metaphysics. Heidegger believes that today’s metaphysics, in the form of technology and the calculative thinking related to it, has become so pervasive that there is no realm of life that is not subject to its dominance. It imposes its technological-scientific-industrial character on human beings, making it the sole criterion of the human sojourn on earth. As it ultimately degenerates into ideologies and worldviews, metaphysics provides an answer to the question of the being of beings for contemporary men and women, but skillfully removes from their lives the problem of their own existence.
Moreover, because its sway over contemporary human beings is so powerful, metaphysics cannot be simply cast aside or rejected. Any direct attempt to do so will only strengthen its hold. Metaphysics cannot be rejected, canceled or denied, but it can be overcome by demonstrating its nihilism. In Heidegger’s use of the term, “nihilism” has a very specific meaning. It refers to the forgetfulness of being. What remains unquestioned and forgotten in metaphysics is Being; hence, it is nihilistic."