He's sitting. Just sitting. If you wanted you could compartmentalize the act. The angle of the knees; the extended arm propping up columns (if required); the center of gravity just so; the heart beating; the shallow breathing; metabolism; catabolism; mitosis; entropy; nail growth; hair recession; sense perception; consciousness; self-consciousness; a large body of mass warping space-time, preventing his floating away; his bottom touching something. The details tend not to matter too much when you, and when someone says you they sometimes mean we, have decided that one thing is this and not that and all else that need not be mentioned when commenting on this thing wrapped in a finely delineated border can all be abstracted away into nothingness. Nothing used to be called ether because light needed something to pass through. Dark matter is the new ether, but this time around light can't have its way with it. When you're sitting and all else is still, nothing is still nothing no matter what you call it. That's just the way it is.