We proceed to the third article thus:
1. It seems that God does not provide for all things directly. We must ascribe to God whatever dignity requires, and the dignity of a king requires that he provide for his subjects through the medium of ministers. Much more, then, does God provide for all things through some medium.
2. Again, providence ordains things to their end. Now the end of anything is its perfection and good, and every cause directs its effect to its good. Hence every active cause achieves the aim of providence. Secondary causes would therefore be done away, if God provided for all things directly.
3. Again, Augustine says [Enchirid.17): "it is better not to know some things than to know them," e.g., trivial things. The philosopher says this also in 12 Metaph., text 51. Now whatever is better must be attributed to God. Hence God does not have direct foresight of anything trivial or evil.
On the other hand: it is said in Job 34:13: "Who hath given him a charge over the earth? or who hath disposed the whole world?"  And on this Gregory comments (24 Moral.26): "God himself rules the world which he himself has made."
I answer: providence includes two things, namely, the reason for the order in things ordained to an end, and the execution of this order, which is called government. Now God provides the first of these directly for all things, since the reason for all things, even for the most trivial, lies in the divine intellect. Moreover, to whatever causes God provides for any effects, he gives the power to produce them. The order of these effects must therefore have been in God's mind beforehand. But divine providence uses certain media in carrying out this order, since it directs lower things by means of higher things. This is not due to any defect in God's power. It is due to his abundant goodness, whereby he confers the dignity of causality even upon creatures. These considerations rule out the view of Plato, quoted by Gregory of Nyssa (8 De Providentia, 3), which supposed three kinds of providence.1. The providence of the highest deity, which provides first and principally for spiritual things, and through them provides genera, species, and universal causes for the whole world.2. The providence which provides for such individuals as come to be and pass away, which he attributes to the gods who encircle the heavens, i.e., to the separate substances which move the heavenly bodies in a circle.3. The providence which watches over human affairs. This he attributes to demons, which the Platonists place betwixt ourselves and the gods, as Augustine tells us (De Civ. Dei.9, ch.1-2; 8, ch.14).
On the first point: the dignity of a king requires that his dispensations be carried out by ministers. But his ignorance of how they do it is a defect, since a practical science is the more perfect the more it takes account of the details of what it achieves.
On the second point: the directness with which God provides for all things does not do away with secondary causes, which are the means by which his ordinances are carried out, as we said in Q.19, Arts.5, 8.
On the third point: it is better for us not to know evil or trivial things, because they hinder us from contemplating better things. But it is not so with God. God sees all things in one intuition, and his will cannot be turned to evil.
 Migne: "What other hath he set over the earth, or whom hath he put in charge of the world which he hath made?"