Discussing Martin Heidegger’s Being and Time (1927), mostly the intro and ch. 1 and 2 of Part 1.
When philosophers try to figure out what really exists (God? matter? numbers?), Heidegger thinks they’ve forgotten a question that really should come first: what is it to exist? He thinks that instead of asking “What is Being?” we ask, as in a scientific context, “what is this thing?” This approach then poisons our ability to understand ourselves or the world that we as human beings actually inhabit, as opposed to the abstraction that science makes out of this.