to wit, as one fails to judge rightly through contempt or neglect of
those things on which a right judgment depends. It is therefore
evident that thoughtlessness is a sin.

Reply Obj. 1: Our Lord did not forbid us to take thought, when we
have the opportunity, about what we ought to do or say, but, in the
words quoted, He encourages His disciples, so that when they had no
opportunity of taking thought, either through lack of knowledge or
through a sudden call, they should trust in the guidance of God
alone, because "as we know not what to do, we can only turn our eyes
to God," according to 2 Paral. 20:12: else if man, instead of doing
what he can, were to be content with awaiting God's assistance, he
would seem to tempt God.

Reply Obj. 2: All thought about those things of which counsel takes
cognizance, is directed to the formation of a right judgment,
wherefore this thought is perfected in judgment. Consequently
thoughtlessness is above all opposed to the rectitude of judgment.

Reply Obj. 3: Thoughtlessness is to be taken here in relation to a
determinate matter, namely, that of human action, wherein more things
have to be thought about for the purpose of right judgment, than in
speculative matters, because actions are about singulars.
_______________________

FIFTH ARTICLE [II-II, Q. 53, Art. 5]

Whether Inconstancy Is a Vice Contained Under Imprudence?

Objection 1: It would seem that inconstancy is not a vice contained
under imprudence. For inconstancy consists seemingly in a lack of
perseverance in matters of difficulty. But perseverance in difficult
matters belongs to fortitude. Therefore inconstancy is opposed to
fortitude rather than to prudence.

Obj. 2: Further, it is written (James 3:16): "Where jealousy [Douay:
'envy'] and contention are, there are inconstancy and every evil
work." But jealousy pertains to envy. Therefore inconstancy pertains
not to imprudence but to envy.

Obj. 3: Further, a man would seem to be inconstant who fails to
persevere in what he has proposed to do. Now this is a mark of
"incontinency" in pleasurable matters, and of "effeminacy" or
"squeamishness" in unpleasant matters, according to _Ethic._ vii, 1.
Therefore inconstancy does not pertain to imprudence.

_On the contrary,_ It belongs to prudence to prefer the greater good
to the lesser. Therefore to forsake the greater good belongs to
imprudence. Now this is inconstancy. Therefore inconstancy belongs to
imprudence.