There are many metaphors for human willpower.
About ten years ago the hot metaphor for willpower among psychologists was a battery. Ego Depletion Theory, advanced by Dr. Roy Baumeister, treated willpower as a finite resource; one that could be spent only so much before it had to be recharged.
Baumeister’s theory has since fallen out of favor; the battery metaphor alone can’t capture the nature of willpower, so people rely on others as well. A few others I’ve seen:
- Force (“All obstacles broke under the sheer force of her will.”)
- Heat (“His eyes were burning with determination.”)
- Light (“She was laser-focused on her goals.”)
Metaphors are limited by nature, highlighting one aspect of a thing while obscuring others. The big question regarding metaphors isn’t whether they are correct. It is whether (and when, and how) they are useful.
For example, the “willpower is a battery” metaphor is useful when you are trying to economize commitments. It is less useful when you need to give a single, intense push to overcome a difficult barrier, like getting through the first few days without a cigarette.
The most useful personal metaphor I have found for willpower — the one that helps me confront and overcome obstacles — is less common. But it’s one we all learned about in high school physics; momentum.