Courage is not simply one of the virtues, but the form of every virtue at the testing point, which means, at the point of highest reality. A chastity or honesty, or mercy, which yields to danger will be chaste or honest or merciful only on conditions. Pilate was merciful till it became risky.

C.S. Lewis (1898-1963) English writer and scholar [Clive Staples Lewis]

The Screw-Tape Letters, #29 (1942)
    (Source)

See Johnson.