Progressives love to boast of their “nuanced” approach to public affairs. Things are not always black or white, they insist. Sometimes they’re gray. Why, then, do so many progressives want a categorical prohibition of torture? Are there no circumstances in which torture would be permissible? Do we want to ban torture even in those cases where it is necessary to save thousands of lives? This column by law professor Alan Dershowitz gets to the heart of the matter.