The reason, therefore, why any event occurs, or, that it passes from the category of the possible into that of the actual, is that God has so decreed. The decrees of God, therefore, are not many, but one purpose. They are not successively formed as the emergency arises, but are all parts of one all-comprehending plan. This view of the subject is rendered necessary by the nature of an infinitely perfect Being. It is inconsistent with the idea of absolute perfection, that the purposes of God are successive, or that He ever purposes what He did not originally intend; or that one part of his plan is independent of other parts. It is one scheme, and therefore one purpose.

Charles Hodge, Systematic Theology, Vol. 1, 538.