Plantinga's Ontological Argument

6. Pruss on Possibility of Maximally
Great Being

Book cover: The Many-Faced Argument by John Hick and Arthur C. McGill (eds)

I argued in section §3 above that Plantinga's premise (29), that it's possible that maximal greatness is instantiated, is necessarily false. In §5, I tried to show that even if (29) is not known to be false, it is not rational to accept it as true. Pruss [2010] has put up a valiant argument for increasing the epistemic probability that (29) is true above even chances. Basically, Pruss [2010: 233f] argues that if a proposition, such as that there is a maximally great being, centrally motivates individuals or communities to lead flourishing and intellectually sophisticated lives, then that proposition is probably true.

There is much to disagree with in his development of his argument. However, here I want to focus on a core difficulty as it touches Plantinga's version of the ontological argument. Pruss devotes the final section of his essay to the objection that what motivates theists in particular is not the modal aspect of the concept of a maximally great being. If this objection is valid, it seriously undercuts the essay's relevance to and support of Plantinga's thesis. As Pruss [2010: 246] states the objection:

. . . while the belief that there actually is a maximally excellent being is central to the lives of flourishing theists, the belief that there is a maximally excellent being in all worlds is not central to the lives of flourishing theists.

Pruss argues that this objection is based on a misreading of Plantinga's argument. He [2010: 246] claims that Plantinga was not 'stipulating that a maximally great being is one that exists in all worlds and is maximally excellent in them all'. Plantinga, Pruss [2010: 247] asserts, only argued that maximal greatness, as a matter of fact, logically entails maximal excellence in all possible worlds. This avoidance of definitional equivalence, according to Pruss [2010: 247], then leaves the 'intellectually sophisticated' theist to 'believe that there is a maximally great being—say, a being that has all perfections—without believing that there is a being that has maximal excellence in every world'.

Firstly, I think Pruss, himself, has misunderstood Plantinga. In his The Nature of Necessity, Plantinga early on [1974: 205] prescribed that 'the term "God" simply abbreviates the longer phrase "the being whose greatness in some world or other is nowhere exceeded"'. As 'world' is meant here in the sense of 'possible world', Plantinga had already semantically tied the concept of 'God' as a maximally great being to a modal framework. This semantic cementing is continued a little later where, in discussing Anselm, Plantinga [1974: 212] declares that 'necessary existence . . . must be considered in comparing a pair of beings with respect to greatness'. This 'must' for Plantinga arises not from an empirical investigation of maximally great beings we might find, but from reflection on what it means to be 'great'. Following some more reflection on the quality of greatness, Plantinga [1974: 214] goes on to stipulate thus:

. . . we might say that the excellence of a being in a given world W depends only upon its (non world-indexed) properties in W, while its greatness in W depends not merely upon its excellence in W, but also upon its excellence in other worlds.

In constructing a simpler version of his ontological argument, Plantinga [1974: 216] made clear what he meant by 'greatness': 'Let us say that unsurpassable greatness is equivalent to maximal excellence in every possible world.' Plantinga continued his semantic coupling of the two notions of 'greatness' and 'necessary existence' in his later God, Freedom and Evil. Here again, Plantinga [1975: 107] stipulated unequivocally what he meant by 'greatness':

A being's excellence in a given world W, let us say, depends only upon the properties it has in W; its greatness in W depends upon those properties but also upon what it is like in other worlds.

Further, Plantinga [1975: 109] regarded his two analytic premises concerning maximal greatness and maximal excellence as 'consequences of a definition—a definition of maximal greatness'.

Book cover: The Nature of Necessity by Alvin Plantinga

So, I think a fair reading of Plantinga shows that for Plantinga, the twin properties of necessary existence and maximal excellence in every possible world are not surprising logical entailments from the concept of maximal greatness. The latter entails the two former properties because of what Plantinga makes 'maximal greatness' mean. The situation here is akin to how the proposition, 'John is a bachelor', entails 'John is not married to Jane or Kate'. Now, 'bachelor' does not mean 'not married to Jane or Kate'. However, the former proposition entails the latter precisely because of what the word 'bachelor' means. If someone accepted the former proposition but rejected the latter, we would say that they are assuming a different meaning of the word 'bachelor'.

The same can be said for Pruss's intellectually sophisticated theistic community. For Pruss [2010: 247], a member of this community 'can believe that there is a maximally great being—say, a being that has all perfections—without believing that there is a being that has maximal excellence in every world'. Sure, but then that theist is using the term 'maximally great being' with a different sense than what Plantinga articulated in his modal version of the ontological argument.[4]

Recall, Pruss intended his essay to be a defence of Plantinga's modal version of the ontological argument in particular. Pruss [2010: 233] writes unequivocally of Plantinga's modal version:

The main controversial premise is the possibility premise (2). I will now offer a new way to make the possibility premise epistemically probable. If it is epistemically probable, then the conclusion of the argument is also epistemically probable, and hence probably there is a maximally great being.

By then shifting the meaning of 'maximally great being' away from Plantinga's intended meaning, Pruss's argument fails to hit the mark. In the place of Plantinga's meaning, Pruss [2010: 247] substituted 'a being than which a greater cannot be conceived or one that has all perfections'. It is precisely these kinds of highly philosophically problematic definitions that Plantinga [1974: §2, 3, 6 and 7] explicitly rejected. Plantinga's modal version of the ontological argument was supposed to avoid the fatal flaws of earlier renditions of the ontological argument that relied on these definitions.

Pruss's semantic decoupling of the term, 'maximal greatness', from 'maximal excellence in every possible world' has robbed his argument of any potency it might have had. By disowning the modal properties of Plantinga's term, 'maximal greatness', Pruss's argument bears no relevance to Plantinga's modal version of the ontological argument. In trying to increase the probability of the possibility of Pruss's kinds of 'maximally great being', Pruss has left the possibility of Plantinga's God untouched.


  1. [4] That Pruss has misconstrued Plantinga's argument is also evidenced by his casting doubt on Plantinga's [1974: 214] premises (34) and (35); two premises that are not seriously in contention in the philosophical literature. Pruss [2010: 247] writes: 'Thus, while I initially said that it is the possibility premise (2) that is the main controversial premise, nonetheless premise (1) is a genuinely substantive though plausible claim about what maximal greatness in fact entails, a premise that can also be disputed.'

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