What did Martin Heidegger mean by “ontology?”
The term “ontology” refers to the study of being in a general sense that is relevant to all thinkers and theorists. Empiricists, for example, have ontologies in that there are some entities that they believe exist. According to Heidegger, ontology, as the first and last subject of philosophy, is the study of Being, with a capital “B.” Being is existence itself, including everything that exists, but in particular human consciousness for which Being is first and foremost the condition of its own being.
For readers who find this confusing, excellent relaxation can be found in Günter Grass’ 1963 novel, Dog Years, which contains a parody of Heidegger’s terminology in the literal description of a canine’s wanderings during the Nazi era. For the more scholarly inclined, there is Theodor Adorno’s The Jargon of Authenticity (1973).