Concluding our close reading for the moment of Heidegger's Being and Time, now up to chapter 3, sections 15 and 16.
These sections are entirely focused on H's primordial ontological category of Being: "ready to hand," or equipment. Since we are primarily action-oriented beings, then, the world is not a set of present-at-hand objects all laid out before us (as H. alleges that Aristotle and science and everyone else has always thought), but is a background "world" in which we act. But this world is not just an undifferentiated mass either; it's made up of tools, like even our own body, which we don't "encounter" (i.e. focus on as a distinct object that needs to be explicitly understood) unless something goes wrong with them.