God's being is from eternity and is immutable, for He has no beginning and in Him nothing begins. His whole being is one act; that is, He is eternal actuality and activity. But He is the beginning, the principium [beginning, principle]. From Him whatever has a beginning sets forth. Created things have a beginning and in them something constantly has its beginning, and this is their major dissimilitudo [greater unlikeness] to the divine being.
Edith Stein, Potency and Act, Redmond, tr., Institute of Carmelite Studies (Washington, DC: 2009), p. 128.