X. The decrees of God can be regarded in two ways: either subjectively (if it right so to speak, i.e., on the part of the internal act in itself and absolutely); or objectively, extrinsically and relatively with respect to creatures (respectively). In the former manner, they do not differ from God himself and are no other than God himself decreeing. But in the latter, they do differ because they may be conceived as many and various (not as to the thing, since God has decreed all things by one single and most simple act, but as to the objects), even as the knowledge of God is conversant with him innumerable objects without detriment to his unity.
XI. The decrees of God are free, not absolutely and as to the principle, but relatively and objectively and as to the end. For there could be no external object necessarily terminating to the divine will, for God stands in need of nothing out of himself. Therefore they could be and not be. But this does not hinder them from being called necessary as to the principle and internal act because the act of intelligence and will could not be absent from God at all. He could not be God without intelligence and will. They are necessary, therefore, as to internal existence, but free as to external relation (schesin) and habit. Nor can the will of God be said to cease absolutely, but with respect to the external object on which it is terminated.
What is the relation of God to His decrees? On the one hand, it consists of God decreeing something freely, and thus they seem to be on the side of God ad extra. On the other hand, they are the expression of God's mind and will, which are constitutive of God ad intra. But certainly nothing can be both internal and external to God at the same time, can it?
As Turretin states, the decrees, coming from God's "intelligence and will" is internal to God. But the decrees, as they are freely done by God, is free in its external relations (schesin). But what does this actually mean?
Perhaps to re-phrase for the intention of clarification, we can think of the decrees as being a thing X, which exists. The existence of X comes about from mind and will, and thus it is eternally timeless, partaking of the eternity of God's mind and will. The quiddity (or "what-ness") of the decrees, of the thing X, is internal to God, for God's mind and will necessitates it.
At the same time, the content or relation of the decrees, the thing X, is external to God, for it terminates upon the things decreed. Thus, the decrees are truly free in this sense, towards things external to the being of God. Thus, the decrees as to its reality is internal to God, God ad intra, yet the decrees as to what they refer to are external to God's being, God ad extra.
Therefore, the decrees of God are one, in the being of God, for God is simple and indivisible. When we speak therefore of the decreeS of God, we have already moved to the ad extra aspect of theology proper. The decrees of God in its one simple ad intra form we know that it exists (quiddity), but not as to what it is. When we inquire into what it is, what they are, we only see the decrees as they are of God's work, in a manner we can understand.