 What am I? What sort of things, metaphysically speaking, are you and I and other human people? What are our fundamental properties, in addition to those that make us people? What, for instance, are we made of? Are we composed entirely of matter, as stones are, or are we partly or wholly immaterial? Where do our spatial boundaries lie, if we are spatially extended at all? Do we extend all the way out to our skin and no further, for instance? If so, what fixes those boundaries? Are we substances—metaphysically independent beings—or is each of us a state or aspect or activity of something else?