First, as Hume noted, the mind always seems to have something going on-some perception or another. Hence, a man is never really thinking about nothing-there is always something in the blender. Second, it could be argued that unlike a blender, a mind cannot engage in its function without some content. Thinking might be more like cutting-while one can make a motion with scissors, they are not cutting unless they have something to cut.
In the case of doing nothing, a man could be doing nothing in the sense that a blender could be blending nothing. Of course, the obvious reply is that while the blender is blending nothing, it is not actually doing nothing. After all, by doing it is doing something. Even thinking about nothing would be doing something, namely thinking about nothing. As such, as long as a man is doing, then he would be doing something-at the very least he is doing. What he is doing, of course, might not amount to much-hence we could be forgiven if we exaggerate and say we are doing nothing.
Earlier on he sort of waves away Heidegger and Sartre, but this seems to me one area where continental philosophy has a lot to offer. (Warning: If there’s a way to talk about this stuff without sounding like sort of a pretentious ass, I haven’t found it yet. Excuse the dorm room philosophizing.) If I’m remembering my Sartre correctly, he argued that the self (“essence”) was, at its core, this endless void containing only a self-annhilating, ever-changing miasma. We are nothing but we can’t think nothing, so we’re willfully imprisoned by our own cognition until the day we die.
It’s not the sunniest view of the mind, and contemporary neuroscience would seem to undermine Sartre’s strident dualism*, but I think there’s a kernel of psychological acuity here. Counscious thought may be only a sheer gauze stretched over our vast animal subconscious, but it’s still the only part of my own mind I can directly experience. And unless I’m sleeping, it never really stops chattering away and gumming up the works of my subconscious processes. There are obviously tremendous advantages to conscious thought, but it’s also the source of a sadness which I suspect is unique to persons. We have a lot of ways of trying to run away from it, or at least temporarily dampen its effects, but we can never be rid of it — a conscious mind can’t even understand what it means to be unconscious.
As far as how one deals with that, I think David Foster Wallace has got the right idea. Recently I went back and reread his commencement speech to Kenyon University. If you haven’t checked it out yet, you should.
*Sartre took this so far he wound up arguing, ludicrously, that physical processes play no role in sexual desire.