Many people insist that their commitments to certain values (e.g. love, honor, justice) are absolute and inviolable - in effect, sacred. They treat the mere thought of trading off sacred values against secular ones (such as money) as transparently outrageous - in effect, taboo. Economists insist, however, that in a world of scarce resources, taboo trade-offs are unavoidable. Research shows that, although people do respond with moral outrage to taboo trade-offs, they often acquiesce when secular violations of sacred values are rhetorically reframed as routine or tragic trade-offs. The results reveal the peculiar character of moral boundaries on what is thinkable, alternately punitively rigid and forgivingly flexible.