We say that we “decide” to get married, to have children, to live in particular cities or embark on particular careers, and in a sense this is true. But how do we actually make those choices? One of the paradoxes of life is that our big decisions are often less calculated than our small ones are. We agonize over what to stream on Netflix, then let TV shows persuade us to move to New York; buying a new laptop may involve weeks of Internet research, but the deliberations behind a life-changing breakup could consist of a few bottles of wine. We’re hardly more advanced than the ancient Persians, who, Herodotus says, made big decisions by discussing them twice: once while drunk, once while sober.