Firmness of spirit. As a virtue, it is a steadiness of will in doing good in spite of difficulties faced in the performance of one's duty.
There are two levels to the practice of fortitude: one is the suppression of inordinate fear and the other is the curbing of recklessness. The control of fear is the main role of fortitude. Hence the primary effect of fortitude is to keep unreasonable fears under control and not allow them to prevent one from doing what one's mind says should be done. But fortitude or courage also moderates rashness, which tends to lead the headstrong to excess in the face of difficulties and dangers. It is the special virtue of pioneers in any endeavor.
As a human virtue, fortitude is essentially different from what has come to be called animal courage. Animals attack either from pain, as when they go after humans because they are angered, whom they would leave alone if they were unmolested. The are not virtuously brave, for they face danger from pain or rage or some other sense instinct, not from choice, as do those who act with foresight. True courage is from deliberate choice, not mere emotion. (Etym. Latin fortitudo, strength; firmness of soul; courage of soul.)