Thomas Aquinas, Compendium of Theology

In the light of the foregoing, it is clear that, although God's government of things is effected through the agency of secondary causes, as far as the carrying out of His providence is concerned, yet the plan itself or ordination of divine providence extends directly to all details. In arranging all matters from first to last, God does not turn over to others the disposal of the final particulars. Men act thus because of the limitations of their knowledge, which cannot at any one time take in many items. This is why higher rulers personally take charge of great concerns, and entrust the management of unimportant affairs to others. But God can take cognizance of a multitude of things simultaneously, as was indicated above. Hence the fact that He attends to the slightest details does not keep Him from organizing the weightiest matters.