The classical inquiry
Courage in the Greek tradition translates andreia — etymologically "manliness," but already in the philosophical literature understood as the virtue that holds firm in the presence of fear, and (in some treatments) in the presence of anger and dishonour as well. The classical inquiry asks both what courage is and how it is distinguished from things that look like courage but are not.
The locus classicus is two-fold. Plato's Laches is the dialogue devoted to the question — the two old generals after whom the work takes its name try to define courage and the dialogue ends in the characteristic Socratic aporia, the productive deadlock. The Aristotelian treatment in the Nicomachean Ethics gives courage as a virtue of character lying in a mean between the failings of rashness (excess of confidence) and cowardice (excess of fear), and restricts the central case to courage in the face of a noble death — most particularly in war.
The older substrate, against which both philosophical treatments are written, is the Homeric. Achilles and Hector and the framing question of how a person bears himself in extremity are already there in the Iliad and shape the vocabulary the philosophers inherit.
What the tradition adds
The Stoic tradition keeps courage among its four cardinal virtues and reads it less narrowly as the bearing of every difficult thing that comes to a life, not only the bearing of physical danger. The Roman fortitudo and virtus inherit and extend this. The Christian tradition receives the four classical virtues as the cardinal virtues — prudence, justice, fortitude, temperance — and adds the three theological virtues. Aquinas treats fortitude carefully in the Summa Theologiae, retaining the connection to facing death well.
Why it matters for Virtue & Power
Courage is the virtue that the classical tradition tends to discuss in concrete cases — battles, trials, public deliberations — rather than in the abstract. The platform follows the texts in that respect: the entries on the Iliad, on war and peace, and on the Socratic refusal at the trial to do an injustice in order to save his life are all entries on courage by another name.