The very ‘beginning’ when God made the heaven and the earth, [some] will construe as if it meant something substantial and embodied, to be regarded as Matter. We, however, insist on the proper signification of every word, [and say] that principium means beginning, - being a term which is suitable to represent things which begin to exist. For nothing which has to come into being is without a beginning, nor can this its commencement be at any other moment than when it begins to have existence. Thus principium, or beginning, is simply a term of inception, not the name of a substance.
Against Hermogenes, ch. 19.