Good food for thought. I'd like to hypothesize that willpower is not limited in a fixed sense, but also not unlimited. (This might be obvious, but worth thinking through.)
Willpower seems to be increased by practice. People who are disciplined seem to have more willpower to apply to a given problem.
Hmm... alternative hypothesis: is it that they have more willpower, or does their discipline - their daily habits of work and self-improvement - mean that they're wasting much less energy on deciding whether to do something, many times each day? It's probably much more energy-efficient to just do something than to keep procrastinating - i.e. to decide to put it off another 5 min, hour or day, again and again.
[I just noticed I'm conflating energy and willpower... and that I don't have a clear definition of willpower.]
Re John Maxwell IV's point, earlier in this discussion, that willpower being seen unlimited could be a useful reinforcer - I can see that it would be a useful thought to psyche myself up, but I'd bet that it's a false belief. An optimally useful belief might be to have an accurate estimate of my own willpower, and to work on the basis that it might be at the high end of the estimated range - so I push myself, but also recognize my need for recovery, and don't exhaust myself.
Why don't I think willpower is unlimited? I heard of a study* where people who have have been making decisions are less able to resist unhealthy snacks. This fits with my experience and that of others I've talked with. (To try and be thorough, an alternative hypothesis of the study could be that making decisions increases the body's desire or need for glucose - a related but not identical claim. I know which hypothesis makes more sense in my own experience, but I'd like to know if there's more solid evidence.)
Please point out errors & help reduce the fuzziness of this argument.
** I just noticed the formatting here - writing John Maxwell IV with the underscores instead of spaces turns out as John_Maxwell_IV
I think this whole reasoning about willpower as a energy (whether renewable or not) is horribly confused. It is just a surface analogy taken too far. For physical work we have muscles that burn calories -- that is a scientific fact. Mental work can also make us kind of "tired", but that is not enough to conclude that we have some analogical mental muscles that burn mana points or whatever.
A big difference is that unlike physical work, mental work does not make us literally tired, but more like frustrated. One can think about pleasant things all d...
I recently read this book. I've tried to summarize the main points below -- you can read my notes here (MSWord doc). You might also find Derek Sivers' notes useful, which can be found here.
NOTE: The general model of willpower (as a finite resource consumed with use) used in this book does not seem to represent a scientific consensus -- see the comments for more detail.
General Claims
Willpower Depletion
Restoring Willpower
Miscellaneous
I declare Crocker's Rules.
[i] I didn’t see enough evidence to conclude whether the cravings are actually stronger, or people are simply less able to resist them, or both. The book claims that both are true.
[ii] The book seems to imply this mental nagging costs willpower, but I don’t recall it being explicitly stated. GTD is also mentioned, and the lack of Next Actions which one has the materials to execute being included in plans causing people to procrastinate. (p. 79)
[iii] The relevant experiment was conducted in a laboratory, so there is no possibility of the experimental results being affected by the fact that people with more self-control may keep their house cleaner. Self-control was measured in ways like being willing/unwilling to week for a larger sum of money instead of receiving a smaller sum immediately, and choosing healthier foods over sugary snacks.
[iv] I wonder if this means that people are more likely to ignore opportunity costs.
[v] ‘Conserving willpower’ is also mentioned around here, which seemed to imply that effective precommitment helped reduce the willpower costs of overcoming constant temptation by making the decision easier.