is from page 63 of GMU professor (and my graduate advisor) Chris Coyne’s 2013 book Doing Bad by Doing Good: Why Humanitarian Action Fails:

The core economic question is how decisions are made about how scarce resources will be allocated among competing uses.  Scarcity necessitates choice, which in turn implies trade-offs since one use of scarce resources precludes another.

The fact resources are scarce is simply due to the face we do not live in Eden.