De Moor IV:26: Immutability Applied to God's Intellect and Will
γ. The same Immutability pertains to the divine Intellect, understanding all things eternally, and Will; since Intellect and Will do not really iffer from Essence in the Perfectly Simple God. Immutable also,
a. Is the divine Intellect, because it is Independent of its objects, and so not subject to their mutations; instead, the divine Intellect itself is the unchanging measure of mutable things. “Certainly,” says the Most Illustrious VRIESIUS, Exercitatione Rationali XVIII, § 4, “as the eye regards various circuits of a revolving wheel without regard to any rotation of its own; so also the divine mind, having no experience of mutation, suffers no mutation from things disturbed by mutations.” Our AUTHOR observes that this Immutability of the divine Understanding and Knowledge is wrested, both by the Jesuits and Remonstrants, attributing to God Middle Knowledge, which will be expressly confuted in § 38, 39, and by the Socinians and Vorstius, in their denial of Prescience of Contingent things, which controversy is considered in § 36.
b. The Immutability of the divine Will, against the Socinians; the Jesuits; Vorstius in his book de Deo, page 312, and in Exegese Apologetica, chapter XI, whose opinion on ths matter TRIGLAND recounts in Kerckelycke Geschiedenissen, volume 4, pages 576, 604b, 609a; and the Remonstrants, will be developed at greater length in Chapter VI, § 9-11, while they in turn, by attributing an Antecedent and Consequent Will to God, together with the perpetual Indifference of God and of all things, destroy that Immutability of Will: consult TURRETIN, Theologiæ Elencticæ, locus III, question XVI; MARESIUS, Systemate Theologico, common place II, § 47; TRIGLAND, Antapologia, chapter XIX, pages 293-298. It is now able to be observed in a word, that the divine Will is altogether Simple. That is, it is one and the same Act, with the variety of the manifold objects not withstanding, and indeed not diverse from the Essence of the Willing God. For the previously asserted Simplicity of God does not permit anything to be given in God that is not Himself. Neither is it to be objected that the Volition of God necessarily differs from His Essence in actuality, since His Essence is not free, as His Volition is, but necessary: for the act of willing exists in God necessarily, although the termination of that necessary act unto this or that object is free and indifferent, falling out in accordance with itself. From this the Immutability of the divine Will follows now of itself: for, what is perfectly simple, and is one and the same with Immutable Essence; it is necessary that it, with the same Essence remaining, is not able not to remain the same and unchanged.
 Francis Turretin (1623-1687) was a Genevan Reformed theologian of Italian descent. After studying at Geneva, Leiden, Utrecht, Paris, Saumur, and Montauban, he was appointed as the pastor of the Italian refugee congregation in Geneva (1648), and later Professor of Theology at the academy (1653). His Institutio Theologiæ Elencticæ has been heavily influential in the Reformed tradition, shaping Charles Hodge’s Systematic Theology and Herman Bavinck’s Gereformeerde dogmatiek.