1. Ratio Christi at Texas A&M

4. Ontological Argument
Ratio Christi at Texas A&M
Zachary Lawson

5. NATURAL THEOLOGY A Priori A Posteriori
Some Transcendental Arguments
(Kalam, Leibnizian, Thomistic, etc)
Argument from Consciousness
Teleological Argument
Ontological Argument
Historical Arguments
Moral/Axiological Arguments
Argument from Religious Experience
natural theology is the enterprise of providing reasons or arguments for the existence of God independent of revealed scripture. These arguments can be divided in several different ways; one such way is a priori vs a posteriori. Basically, this division says does this come from experience or before experience. In the case of the a posteriori arguments, the starting point is some fact about reality, experience, or the universe. for example, the cosmological arguments start with the fact that the universe had a beginning (kalam), the universe is contingent (leibniz), or that change occurs (thomistic/aristotelian). the teleological arguments start with the fact that the universe appears to be finely tuned for life or that there are apparent patterns of design that need explanation. the moral argument starts with the fact of moral experience and the objective values and duties that are encountered while interacting with other moral agents. AOC starts with the fact that we are conscious minds, historical arguments are based heavily on historical fact and evidence, etc, etc. These are the arguments that most people are familiar with and from this sampling, one can see they are also the most popular. Now, a priori arguments are unique because they do not make any appeals to evidence. These arguments are self contained and exclusively abstract. This is the case with the ontological argument. So, with that in mind, let me tell you a story.

6. underground church story - “what is God?”, creator theology

7. St. Anselm Formulated in the Proslogium
God is defined “the greatest conceivable being”
Existence in reality > existence in mind
Criticism
Guanilo: parody (greatest island)
Kant: existence is not a property
Aquinas: only mental existence deduced
St. Anselm
Searching for a silver bullet: anselm did all that a posteriori stuff but he wanted a single argument
Hence, even the fool is convinced that something exists in the understanding, at least, than which nothing greater can be conceived. For, when he hears of this, he understands it. And whatever is understood, exists in the understanding. And assuredly that, than which nothing greater can be conceived, cannot exist in the understanding alone. For, suppose it exists in the understanding alone: then it can be conceived to exist in reality; which is greater.
Therefore, if that, than which nothing greater can be conceived, exists in the understanding alone, the very being, than which nothing greater can be conceived, is one, than which a greater can be conceived. But obviously this is impossible. Hence, there is no doubt that there exists a being than which nothing greater can be conceived, and it exists both in the understanding and in reality. (1962, p. 8)
Anselm remains in the realm of hypothetical being. It is still the being which has hypothetically the notion of existence which is greater than the hypothetically nonexistent being. All this is true enough but still hypothetical.”

8. Multiple variations over past 1000 years Descartes Leibniz Malcolm
Gödel
Hartshorne
Plantinga
Other Defenders

9. Modal Logic Possible World
A possible (i.e. non-contradicting) state of affairs
Ways the world could have been
Alethic possibility
Necessary
Cannot fail to exist
Exists in every possible world
Contingent
Can fail to exist
Dependent upon something else for its existence
Does not exist in every possible world
Modal Logic

10. Alvin Plantinga’s Modal Ontological Argument
It is possible that a maximally great being (MGB) exists
If it is possible that a MGB exists, then a MGB exists in some possible world
If a MGB exists in some possible world, then a MGB exists in all possible worlds
If a MGB exists in all possible worlds, then a MGB exists in the actual world
If a MGB exists in the actual world, then a MGB exists

11. Valid Argument?

12. A maximally great being exists either in ALL possible worlds or in NO possible worlds.
The Gist

13. Yes! No! Properly basic/apparent Natural Theology Is God Possible?
Ground of necessary truths
No!
Paradoxes/incompatible properties
Logical argument from evil
Metaphysical naturalism
Is God Possible?

14. “Since all efforts to show that the concept of God is contradictory have failed heretofore I conclude, somewhat reluctantly, that God exists…I have not yet seen an even slightly plausible argument [for God’s incoherence]. Until I do, the Ontological Argument will be cogent to me.”
Trent Dougherty
Since all efforts to show that the concept of God is contradictory have failed heretofore I conclude, somewhat reluctantly, that God exists…I realize that to the average person, this seems like a trick, but the average person is not particularly accustomed to following logical arguments at all, much less highly specialized forms of logical calculi developed by professional philosophers. Most professors at the University level don’t even know modal logic and many have never studied it and some have never heard of it. What do those who know it, but don’t believe in God say? They say that the concept of God is incoherent. I have not yet seen an even slightly plausible argument to that effect. Until I do, the Ontological Argument will be cogent to me. - Trent Dougherty

15. Sources and Further Reading
Nature of Necessity by Alvin Plantinga, 1977 [PDF]
A Valid Ontological Argument? by Alvin Plantinga, 1961 [PDF]
Kant’s Objection to the Ontological Argument by Alvin Plantinga, [PDF]
De Re et de Dicto by Alvin Plantinga, 1969 [PDF]
The Ontological Argument: From St. Anselm to Contemporary Philosophers by Alvin Plantinga and Richard Taylor [Amazon]
BWCNT: The Ontological Argument by Robert Maydole [WileyOnline]
The Proslogium by Anselm [PDF]

16. Sources and Further Reading
The Ontological Argument Discussed by Peter S. Williams [MP3]
The Existence of God (23-26) by W. L. Craig [Transcript][iTunes]
The Ontological Argument by Fleetwood Bible Church [iTunes] [PDF]
Overview of the Ontological Argument by InspiringPhilosophy [YouTube]
History of the Ontological Argument [YouTube]