(Pond, at Monroe County Community College)
In my MCCC Philosophy of Religion classes I taught Anselm's Ontological Argument for God's Existence, and modal version of the Ontological Argument. Here is Alvin Plantinga's modal version of the Ontological Argument for God's existence. It is a real head-twister!
Using modal logic, the following is true: If a necessary being is possible then a necessary being exists. (Think about it, modally.)
Or:
1. There is a possible world in which a necessarily existing being exists.
2. Therefore, a necessarily existing being exists.
Note: This argument avoids the Kantian criticism that 'exists' is not a predicate.
Using modal logic, the following is true: If a necessary being is possible then a necessary being exists. (Think about it, modally.)
Or:
1. There is a possible world in which a necessarily existing being exists.
2. Therefore, a necessarily existing being exists.
Note: This argument avoids the Kantian criticism that 'exists' is not a predicate.
PLANTINGA’S MODAL VERSION OF THE ONTOLOGICAL ARGUMENT FOR GOD’S EXISTENCE
The argument goes:
1. It is possible that there is a being (B) that has maximal greatness.
2. So, there is a possible being that in some world W has maximal greatness.
3. A being has maximal greatness in a given world only if it has maximal excellence in every world.
4. A being has maximal excellence in a given world only if it has omniscience, omnipotence, and moral perfection in that world.
5. Therefore, “there actually exists a being (B) that is omnipotent, omniscient, and morally perfect; this being, furthermore, exists and has these qualities in every other world as well.”
5. Therefore, “there actually exists a being (B) that is omnipotent, omniscient, and morally perfect; this being, furthermore, exists and has these qualities in every other world as well.”
Needed to understand this argument:
Logical possibilities and impossibilities do not vary from world to world. If a given proposition or state of affairs is impossible in at least one possible world, then it is impossible in every possible world. For example, "square circles" are logical impossibilities in our world. Therefore they are logical impossibilities in every possible world. There is no possible world, no creatively invented world, that could contain a square circle.
- There are no propositions that are in fact impossible but could have been possible. For example, square circles could not exist in any conceivable/possible world.
- And, there are no propositions that in fact are possible but could have been impossible. For example, if there is a possible world in which SpongeBob exists, then there is no possible world in which SpongeBob could not exist.
- Therefore, B's nonexistence is impossible in every possible world. And because B is a maximally great Being, B exists in every possible world.
- Therefore B’s nonexistence is impossible in this world (since this world is a possible world).
- Therefore B exists and exists necessarily.
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Plantinga's Modal Version Of the Ontological Argument (From Graham Oppy)
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| (Warren Dunes State Park, Michigan) |
Graham Oppy presents Alvin Plantinga's modal version of the ontological argument as follows.
An entity is "maximally great" iff (if and only if) it necessarily exists and possesses "maximal excellence" (i.e., is omnipotent, omniscient, and morally perfect).
Keeping this in mind, note that a maximally great entity cannot be a contingent thing. As regards contingent things, it is possible that a certain contingent thing exists. E.g., it is possible that a unicorn exists (logically possible).
Therefore, regarding a maximally great thing:
1) Either it is not possible that a maximally great entity exists or it is necessary that a maximally great entity exists.
2) It is (logically) possible that a maximally great entity exists.
3) Therefore a maximally great entity exists. (That is, an entity that is omniscient, omnipotent, morally perfect, and possesses these attributes (i.e. is "maximally excellent") in every possible world.)
Oppy frames it this way.
1. There is a possible world in which there is an entity which possesses maximal greatness.
2. (Hence) There is an entity which possesses maximal greatness.
Oppy writes: "Under suitable assumptions about the nature of accessibility relations between possible worlds, this argument is valid: from it is possible that it is necessary that p, one can infer that it is necessary that p."
Note:
1) it is possible that it is necessary that p.
2) Either p cannot possibly exist or p necessarily exists.
3) Therefore (from P1 & P2, using disjunctive syllogism) p necessarily exists.
Oppy's essay on the Ontological Argument in Stanford Encyclopedia of Philosophy is a good one. He goes on to offer criticisms of Plantinga's version. And gives Plantinga's further reflections on the status of the argument.
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The Modal Ontological Argument According to Plantinga
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| (Sterling State Park) |
The Internet Encyclopedia of Philosophy article by Kenneth Himma is good on explaining the Modal Version of the Ontological Argument for God's Existence.. Here is Plantinga's OA for God's existence, via Himma.
Plantinga defines two properties: "maximal excellence" and "maximal greatness."
P1. A being is maximally excellent in a world W if and only if it is omnipotent, omniscient, and morally perfect in W.
P2. A being is maximally great in a world W if and only if it is maximally excellent in every possible world.
"Thus, maximal greatness entails existence in every possible world: since a being that is maximally great at W is omnipotent at every possible world and non-existent beings can't be omnipotent, it follows that a maximally great being exists in every logically possible world." If, then, a maximally great being exists in some possible world, then it exists in every possible world, to include our actual world.
Is it logically possible that a maximally great being exists in some possible world? Plantinga thinks so. To think this is not possible one would have to show that the concept of "maximally great being" is logically contradictory, like "square circle." Therefore, the concept of a "maximally great being" is logically possible; i.e., possibly instantiated. It follows, therefore, that a maximally great being (i.e., God) exists in every possible world.
Himma now formulates Plantinga' argument as follows:
1. The concept of a maximally great being is self-consistent.
2. If 1, then there is at least one logically possible world in which a maximally great being exists.
3. Therefore, there is at least one logically possible world in which a maximally great being exists.
4. If a maximally great being exists in one logically possible world, it exists in every logically possible world.
5. Therefore, a maximally great being (i.e., God) exists in every logically possible world.
As P2 affirms, maximal greatness entails existence in every possible world. If it is possible that such a being exists in one possible world, then it exists in every possible world. Since our world is a possible world, God exists in our world.
See Himma's entire essay for more, including objections.