According To The Teaching of St. Thomas Aquinas
PART FIRST.
THE ORDINARY PRESENCE OF GOD IN ALL CREATURES ¹
Finally, in order fully to convince us that we cannot escape His ever-vigilant eye, God Himself, using our weak human language, with infinite condescension, says to us through the mouth of His prophet: "Shall a man be hid in secret places, and I not see him, saith the Lord? Do not I fill heaven and earth, saith the Lord?" (Jeremiah xxiii. 24.).
It is not necessary to cite other testimonies in proof of a point of doctrine admitted by all who believe in the existence of an infinite Being, the Author of all things; yet, on account of its extreme importance, we should like to set down here the philosophical proof of the omnipresence of God, given by St. Thomas. God, he says, "is present in all things, not as part of their essence, or as an accidental element, but as the active principle is present to the thing on which it acts; for it is essential that the efficient cause be united with the object upon which it exercises an immediate activity, and that it comes into contact with this object, if not bodily, then, at least, by the exercise of its power and energies." (Summa Theologica, I., q. viii., a. 1.)