Objection 1. It seems that providence is not becoming to God. For providence, according to Tully (De Invent. ii), is a part of prudence. But prudence, since, according to the Philosopher (Ethic. vi, 5,9,18), it gives good counsel, cannot belong to God, Who never has any doubt for which He should take counsel. Therefore providence cannot belong to God.
Objection 2. Further, whatever is in God, is eternal. But providence is not anything eternal, for it is concerned with existing things that are not eternal, according to Damascene (De Fide Orth. ii, 29). Therefore there is no providence in God.
Objection 3. Further, there is nothing composite in God. But providence seems to be something composite, because it includes both the intellect and the will. Therefore providence is not in God.
On the contrary, It is said (Wisdom 14:3): "But Thou, Father, governest all things by providence [Vulg. But 'Thy providence, O Father, governeth it.']."
I answer that, It is necessary to attribute providence to God. For all the good that is in created things has been created by God, as was shown above (Question 6, Article 4). In created things good is found not only as regards their substance, but also as regards their order towards an end and especially their last end, which, as was said above, is the divine goodness (21, 4). This good of order existing in things created, is itself created by God. Since, however, God is the cause of things by His intellect, and thus it behooves that the type of every effect should pre-exist in Him, as is clear from what has gone before (19, 4), it is necessary that the type of the order of things towards their end should pre-exist in the divine mind: and the type of things ordered towards an end is, properly speaking, providence. For it is the chief part of prudence, to which two other parts are directed--namely, remembrance of the past, and understanding of the present; inasmuch as from the remembrance of what is past and the understanding of what is present, we gather how to provide for the future. Now it belongs to prudence, according to the Philosopher (Ethic. vi, 12), to direct other things towards an end whether in regard to oneself--as for instance, a man is said to be prudent, who orders well his acts towards the end of life--or in regard to others subject to him, in a family, city or kingdom; in which sense it is said (Matthew 24:45), "a faithful and wise servant, whom his lord hath appointed over his family." In this way prudence or providence may suitably be attributed to God. For in God Himself there can be nothing ordered towards an end, since He is the last end. This type of order in things towards an end is therefore in God called providence. Whence Boethius says (De Consol. iv, 6) that "Providence is the divine type itself, seated in the Supreme Ruler; which disposeth all things": which disposition may refer either to the type of the order of things towards an end, or to the type of the order of parts in the whole.
Reply to Objection 1. According to the Philosopher (Ethic. vi, 9,10), "Prudence is what, strictly speaking, commands all that 'ebulia' has rightly counselled and 'synesis' rightly judged" [Cf. I-II, 57, 6]. Whence, though to take counsel may not be fitting to God, from the fact that counsel is an inquiry into matters that are doubtful, nevertheless to give a command as to the ordering of things towards an end, the right reason of which He possesses, does belong to God, according to Psalm 148:6: "He hath made a decree, and it shall not pass away." In this manner both prudence and providence belong to God. Although at the same time it may be said that the very reason of things to be done is called counsel in God; not because of any inquiry necessitated, but from the certitude of the knowledge, to which those who take counsel come by inquiry. Whence it is said: "Who worketh all things according to the counsel of His will" (Ephesians 1:11).
Reply to Objection 2. Two things pertain to the care of providence--namely, the "reason of order," which is called providence and disposition; and the execution of order, which is termed government. Of these, the first is eternal, and the second is temporal.
Reply to Objection 3. Providence resides in the intellect; but presupposes the act of willing the end. Nobody gives a precept about things done for an end; unless he will that end. Hence prudence presupposes the moral virtues, by means of which the appetitive faculty is directed towards good, as the Philosopher says. Even if Providence has to do with the divine will and intellect equally, this would not affect the divine simplicity, since in God both the will and intellect are one and the same thing, as we have said above (Article 19).
Source: Summa Theologica (New Advent)