/summa/SS/SSIII/SS_Q125:
We must now consider the vices opposed to fortitude: (1) Fear; (2) Fearlessness; (3) Daring.
Under the first head there are four points of inquiry:
(1) Whether fear is a sin?
(2) Whether it is opposed to fortitude?
(3) Whether it is a mortal sin?
(4) Whether it excuses from sin, or diminishes it?