Here is TF Torrance describing John Knox’s view on what Knox called God’s ‘ordinance of Grace’, and how that related to his view of God’s immutability.

John Knox never wearied of affirming the immutability of God. He ever remains the same God, true and faithful to his ‘joyful promise’ to Adam that seed of the woman would break down the serpent’s head. This took the form of an ordinance of grace in which God provided a way within the history of mankind for deliverance and redemption. It is indeed upon the ordinance of grace that the whole order of creation depends, for it remains the same in the midst of man’s sin, and in spite of it, the ordinance of grace assumed the character of the promise. The promise involves judgment — the seeking out of man, his calling, his rebellion and conviction of sin, but throughout all judgment and wrath, through all calamity and disaster, God’s purpose for mankind was being worked out. In the first instance this took historical form in the calling of Israel to be the medium of God’s self-revelation to mankind, and it is that ordinance which proved to be the centre around which all things revolve and in relation to which they cohere. He is the God who brough Israel out of Egypt and destroyed Pharaoh in the Red Sea, who sent the Jews into exile, and brought them back as a remnant into Palestine. God is immutable and his ancient Word still holds sway — his ancient ways still appear in his dealings with man. But this is no immutability conceived in philosophical categories — it is the immutability of God’s purpose, will and action, for God is above all the living God who is at work in his creation, whose hand disposes nations and kingdoms. His divine ordinance of grace took historical shape in his covenanted relations with the people of Israel through whom a way was prepared for its ultimate fulfilment in the Incarnation and in the inauguration of the Church. No theologian has had a more vivid and dramatic or a more powerful realisation of direct divine action in history than Knox, and of its ultimate soteriological character. It is here that his theology stands out in such contrast to medieval teaching — its dynamic outlook indicates that there had taken place a radical move away from the rather static categories of the medieval frame of mind. This is vividly evident in his acceptance of the influence of the Old Testament and its significance for his own times in Scotland. The very same God of whom we learn in the Old Testament Scriptures, not least through the great prophets, and in the New Testament Scriptures in the original mission of the Church, now deals with men and nations through the mighty acts of his saving Word. (Thomas Torrance, “Scottish Theology,” 8-9)

There is alot in this quote. Torrance covers Knox’s themes of a ‘Doctrine of God’, Soteriology, and Eschatology; and he notes how all of these points are shaped by the life of God which is grace. This provides a basis for speaking about God’s activity in salvation history, so that we can have a God who is involved with His creation in dynamic ways; without sacrificing His immutable character. We see how Knox, through Torrance’s commentary, jettisoned the rather static God of medieval scholasticism who only was able to interact with His creation through a demeanor of stasis (or being static); which led to the development of thinking of God through decrees (this way God could remain “unmoved” and thus non-contingent by His creation).

Both Federal and Classic Calvinism are still stuck in the latter mode of understanding God, in other words they try to work through the categories provided by medieval scholasticism; which I think is at odds with scripture. I favor Torrance’s Knox, and his approach.