From a post on EconLog by David Henderson.
The Ten Pillars of Economic Wisdom
By David R. Henderson
1. TANSTAAFL: There ain’t no such thing as a free lunch.
2. Incentives matter; incentives affect behavior.
3. Economic thinking is thinking on the margin.
4. The only way to create wealth is to move resources from a lower-valued to a higher-valued use. Corollary: Both sides gain from exchange.
5. Information is valuable and costly, and most information that’s valuable is inherently decentralized.
6. Every action has unintended consequences; you can never do only one thing.
7. The value of a good or a service is subjective.
8. Creating jobs is not the same as creating wealth.
9. The only way to increase a nation’s real income is to increase its real output.
10. Competition is a hardy weed, not a delicate flower.