Question X: Whether a vow of a thing that can have a good or an evil outcome is valid

D. BONAVENTURE answers in a few words: a thing that can have a good and a bad outcome can be vowed, but under the condition of a good outcome; and that if one vows it without condition, it is indiscreet, and one is not bound to the vow.

WITH REGARD to this, the outcome must be considered at the time when the vow is to be executed, not however the time at which the vow is made: whether the matter is good or not; whether apt or inept. So Sanchez lib. 4. cap. 9. n. 2.

From this it is defined that one who vows an inept thing is bound to observe it once it has been made apt at the time of the intended execution, in which the intention of the one vowing must especially be considered. Hence Navarrus, summa, cap. 12. last num., says that one who vows generally something having a successive course is bound for the time at which the matter is apt for the vow, because the vow comprehends the whole time; but if one vows only for the time at which it is illicit, then it is illicit, he says, with D. Bonaventure.