These admirable short biographies trace a tradition of a philosophy as a way of life. It's no accident that Kant is the only career academic chosen and 20th-century giants are absent; Miller is suspicious of the locking up of the discipline within universities, preferring thinkers out in the world. For Montaigne, Descartes, Rousseau and Nietzsche, just as for Socrates, Plato, Diogenes, Aristotle and Seneca, how a philosopher lived embodied his ideas, so it makes sense to profile them before providing lucid, non-technical summaries of their theories. Miller performs both tasks expertly, and his book gains a novelistic richness as recurring themes emerge. Crises or epiphanies that turn thinking upside down (as with Augustine or Emerson) are frequent, for example; and it's striking how many of the 12 were close to rulers, from the political humiliations of Socrates and Plato, via Seneca advising Nero, to Montaigne negotiating on behalf of Henry of Navarre and Descartes agreeing to be Queen Christina of Sweden's court philosopher.