Pure Being, which has nothing of non-being in itself, is in such wise eternally infinite that no non-being is before it or after it, and it contains within itself all that is or can be. This being is all that it is in the highest measure of being, or more correctly, it is measureless (it is the very measure by which all else is to be measured)- it is pure act. In it nothing is shut, nothing remains unfolded; it is rather in absolute openness, illumined in itself and through itself; that is, it is light itself - it is pure spirit.
-St. Teresa Benedicta of the Cross (Edith Stein)
Potency and Act, conclusion.