I don't have a good theory - it's just based on reading biographies. Almost no famous thinkers lived on passive income (although, as I've said, annuities and bonds have been widely available for over 500 years). And probably not any kind of job will do. The most plausible explanation I've read belongs to Richard Feynman:
> I have to have something so that when I don't have any ideas and I'm not getting anywhere I can say to myself, "At least I'm living; at least I'm doing something; I am making some contribution" -- it's just psychological. When I was at Princeton in the 1940s I could see what happened to those great minds at the Institute for Advanced Study, who had been specially selected for their tremendous brains and were now given this opportunity to sit in this lovely house by the woods there, with no classes to teach, with no obligations whatsoever. These poor bastards could now sit and think clearly all by themselves, OK? So they don't get any ideas for a while: They have every opportunity to do something, and they are not getting any ideas. I believe that in a situation like this a kind of guilt or depression worms inside of you, and you begin to worry about not getting any ideas. And nothing happens. Still no ideas come. Nothing happens because there's not enough real activity and challenge
The sentiment in general is reasonable to me: that humans are generally more effective and more productive when they have something to do and work on, even when they're not getting anywhere with their main project(s).
It's not at all clear to me that a menial job is a strong solution to that problem. I would expect that in, say, a world with UBI, that also recognized this problem, people would find better ways to keep themselves feeling like they are at least doing something and making some contribution, than working on things they don't care about or believe in. There are plenty of meaningful volunteer opportunities in the world that would be much more effective "make you feel useful" solutions than filing papers in a bureaucratic office.
> I have to have something so that when I don't have any ideas and I'm not getting anywhere I can say to myself, "At least I'm living; at least I'm doing something; I am making some contribution" -- it's just psychological. When I was at Princeton in the 1940s I could see what happened to those great minds at the Institute for Advanced Study, who had been specially selected for their tremendous brains and were now given this opportunity to sit in this lovely house by the woods there, with no classes to teach, with no obligations whatsoever. These poor bastards could now sit and think clearly all by themselves, OK? So they don't get any ideas for a while: They have every opportunity to do something, and they are not getting any ideas. I believe that in a situation like this a kind of guilt or depression worms inside of you, and you begin to worry about not getting any ideas. And nothing happens. Still no ideas come. Nothing happens because there's not enough real activity and challenge
http://www.pitt.edu/~druzdzel/feynman.html