So, because I am not the smartest of men, I like to live by simple ideas. "Keep it simple, stupid." is an example of one such idea. Also, as FI has become a more defined goal in my life, I've looked for a good way to trim the philosophy of it to such an idea. MMM has embodied a lot of the specifics, and has offered what he has a philosophy (increase income, use less, save money, make less of a negative impact on the environment).
But as far as a central idea is concerned, "Consume less; create more." seems to work quite well. "Create" in this sense is DIY activities, work, volunteering, art, music, cooking delicious meals - any useful thing really. And consuming is using any kind of resources for oneself.
Unfortunately, at its extremes, it's not tractable. You'll die if you consume nothing. Trying to produce something without consuming the energy needed to create that thing is laughable. Thoughts? Anyone else have a better version?