What Is the Significance of the Phrase, No Free Lunch?

The tetanstafl phrase refers to the idea that scarcity is a universal condition for human choosers. It was popularized by robert heinlin's classic syphi book, the moon is a harshmi ess. Agast ans wy chose it as the unifying theme for his books fallacies. He says opportunity cost reasoning is at the heart of what it means to be an economist.