This work reconstructs humility by tracing a consistent but often unstated definition: humility is a virtue of self-knowledge acquired by the practice of other-centeredness. Humility is a 'meta-virtue', a virtue for acquiring virtue. Humility is a virtue of surpassing importance in Christian tradition, but is largely absent from contemporary moral debate. Humility carries a double resonance for an ethics of virtue. First, humility acts as a virtue of self-knowledge in any realm of human activity. Second, humility clears away pride that derails us from seeking virtue at all, and so plays a role in the acquisition of virtues in general. This work begins with the account of humility offered in the "Summa Theologiae". Next, the Christian tradition of humility is discussed, with Augustine, the desert ascetics and Benedict as primary interlocutors. Humility also has ramifications for moral epistemology: when humility is accepted as a virtue, moral truth is seen to be personal rather than abstract, communal rather than individual, and a matter of process rather than status.