Few of us spend much time thinking about courage, but we know it when we see it - or do we? Is it best displayed by marching into danger, making the charge, or by resisting, enduring without complaint? Is it physical or moral, or both? Is it fearless, or does it involve subduing fear? Abner Small, a Civil War soldier, was puzzled by what he called the mystery of bravery; to him, courage and cowardice seemed strangely divorced from character and will...