Does God Have a Nature? (Aquinas Lecture 44) Paperback – June 1, 1980

nice price for a Plantinga book.

The first half of Plantinga's essay critiques Thomas Aquinas' notion of absolute divine simplicity as embodied in the Identity Thesis: God is his attributes. Plantinga's argument runs something like this (and the numbers in parentheses are my own outline; Plantinga's differs in the book) Thomas said

(1) God's nature is identical with his attributes.

From this Plantinga draws the inference:

(2) God has the properties of life, power, goodness, etc.

Given Thomas' Identity Thesis (1) we can infer

(3) God is the property "life," goodness, etc.

Since divine simplicity precludes God's being made up of parts, we reason

(4) the property life = the property goodness = the property power, etc.
(5) Thus, there is no difference between the properties.
(6) If there is a property with which God is identical, then God is that property [1, 3]
(7) If God is a property, then he is not a person.

So far, so good. We applaud Plantinga's careful argumentation. Unfortunately, he has another agenda. This concerns what kind of nature God has. For example, if eternal truths depend upon God (are contingent upon him), then they are within his control.

(8) God is a se and sovereign.
(9) It is the nature of an a se being to not be dependent on x.
(10) Therefore, Plantinga argues, abstract forms like truth and goodness are not external to God but depend upon him.
(11) God can thus create a world where he knows he doesn't exist.
(12) [11] is absurd.

The above is extreme nominalism and Plantinga rightly argues that it is absurd. However, Plantinga construes the opposite position--Platonic realism--as something which no Christian theist can accept. He argues that the Forms are not dependent upon God for their truth, but are necessarily true. Therefore,

~(13)
The denial that God is sovereign, for their exist a truth independent of his power.

Plantinga steers out of this problem by endorsing Descartes' universal possibilism. I think there is another option for traditional Christians: St Maximus the Confessor. St Maximus said that the one LOGOS is the many LOGOI (I am summarizing key parts from his Ambiguum 7). Collectively, the Forms are LOGOI, which is LOGOS, which is the Second Person of the Trinity. The Logos is revealed and multiplied in the Forms (logoi) which are then recapitulated back into the Logos (Ephesians 1:10). The Logos is the interconnecting cause that holds the Forms together. The Logoi, therefore, pre-exist in God.

Thus, we disagree with Plantinga. It is not the case that affirming what he calls "abstract properties," but which are better known as the Forms, is to posit a realm of truth outside of God's nature and control. But rather, the Forms--viewed through the prism of St Maximus the Confessor--are God, or more particularly, they are the manifestation of Logos.

Conclusion:
Few in the Reformed camp will accept Plantinga's premise that sovereignty/aseity necessarily implies God could create logical absurdities. I think, technically, that it does but few will buy it. His argument against Platonic realism is a bit stronger. The book is painfully written, though the argument is somewhat easy to follow.

Could the equation of God's nature with God's characteristics be better understood by considering God dependent on those characteristics? Can the implications of this be avoided if we are not Platonists? Is 2 + 2 = 4 true because of the nature of the universe or independently of it? Could it ever have been false? While this analysis is interesting in its own right I kept finding the dilemma essentially the same as in other inquiries - such as The Nature of Mathematical Knowledge by Philip Kitcher as he considers the evolution of mathematics. While the vocabulary is different the puzzle seems the same. This is interesting because AP uses insights that change the nature of the puzzle somewhat. Post Wittgenstein does the issue change when we consider language games? While AP does not frame the issue in exactly the terms of language games, the puzzle is certainly transformed by these post linguistic turn insights.

The question in the title of this 1980 contribution to Marquette University's Aquinas Lecture series has its root in a broader concern vis-a-vis the Divine omnipotence: If we posit that God has a nature, must we conclude that He has properties different from Himself (say, His own wisdom, or the truths of arithmetic) over which He has no control? Plantinga pursues five lines of inquiry.
First, he investigates the Kantian transcendental idealism of Kaufman, who concludes that God as He is in Himself entirely transcends any concept we have of Him. Plantinga deftly draws out the incoherence of this position: if God transcends all of our concepts of Him, He must also transcend the concept we have of God "God transcends all of our concepts of Him", and the position crumbles into dust.
Second, he considers the position of Aquinas that God is simple: that is, God has a nature but is identical to it, so that He is all of His properties, whence there exists no property external to Him such that He has no control over it. Plantinga is less successful here: He argues that the position leads to the conclusion that God is a property. Since a property can't be a person but is merely an abstract object, he says, it would follow that God is an abstract object. He does briefly consider the Thomist position that what is said of God, as opposed to what is said of us (e.g., goodness, wisdom, intellect, etc.), is said neither univocally nor equivocally, but analogically. After stating that this notion is a difficult one, Plantinga concludes that, rather than simply supporting the notion that "property" is applied to God and to the creation analogically, it "cuts both ways": that is, the notion can be used equally well to cast doubt on our argument for God's simplicity. It is not at all obvious, however, from the fact that the analogical predicate is not minutely spelled out, that it is susceptible to any such desired use. Thus Aquinas' notion of the Divine simplicity remains (despite a few minor difficulties) broadly coherent.
Third, Plantinga takes on nominalism, the belief that abstract objects do not actually exist, but only concrete instantiations of this. He shows masterfully that nominalism doesn't solve the problem: Even if there are no abstract objects, there are truths (if not, assertions of nominalism itself will be unsubstantive). Over some of these (say, that a foot-long hot dog exceeds six inches in length), on the showing of nominalism, God still has no control.
Fourth, he considers the Cartesian notion of universal possibilism, the idea that God has a nature but that none of His properties are necessary--they could all have been otherwise. This, he points out, has the virtues of coherence and of consistency in asserting that everything is under God's control: He could have made anything at all other than it is (three and four could have been eight instead of seven, say). Plantinga goes to great length to elucidate (quite successfully) the ambiguity inherent in this position and goes on to argue that, if is true, it compromises our knowledge of any truth at all.
Fifth, Plantinga honestly accepts what he sees to be the consequence of the failure of the above positions: God has a nature, and His omnipotence is limited by the fact that there are necessary truths over which He has no control. He ends with a line of thought which may conclude that "we can point to an important dependence of abstract truths upon God," but unfortunately he does not develop it here.
In summary, Plantinga is mostly sound and lucid as always, but I am not persuaded to abandon belief in the Divine simplicity. It is well sustained by Thomas' notions of divine eternity, of the creation's asymmetrical relation to God, and of analogical predication, and has the additional virtues (not touched upon by Plantinga) of metaphysical superiority and beauty. These qualities alone bestow upon the notion of the Divine simplicity some warrant (in Plantinga's sense), enough warrant, I say, for knowledge, provided that the notion is coherent and otherwise undefeated.
All told, the book is highly stimulating and well worth reading.