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Is the Modal Ontological Argument for God a Sound Proof?


Over the coming weeks, instead of exclusively posting articles asserting and defending a particular view, we'd also like to feature open-ended discussion posts that lay on the table a popular argument for or against God and then invite us to discuss it together, as a community, in the comment boxes.

Today, we'll begin with Alvin Plantinga's modal ontological argument for God. Plantinga is one of the most respected and influential philosophers today. He's the John A. O'Brien Professor of Philosophy Emeritus at the University of Notre Dame and has written groundbreaking books on the problem of evil, God and science, and philosophical arguments for God.

His modal ontological argument for God relies on modal logic, which deals with the logic of possibility and necessity. Watch the nine-minute video below for a summary of the argument:

The video presents the argument like this:

Premise 1: It is possible that God exists.
Premise 2: If it is possible that God exists, then God exists in some possible worlds.
Premise 3: If God exists in some possible worlds, then God exists in all possible worlds.
Premise 4: If God exists in all possible worlds, then God exists in the actual world.
Premise 5: If God exists in the actual world, then God exists.
Conclusion: Therefore, God exists.

What's interesting about this argument is that it attempts to show that if God's existence is merely possible, then it would be necessary. Or to put it another way, the only way God couldn't exist is if his existence is impossible. Thus if Plantinga is right, any atheist who says "I don't believe God exists but it's at least possible" would, if he properly understands the argument and Plantinga's definition of God, be logically compelled to change his mind.

If the argument holds, it would also mean we can't say there's a 50%/50% chance of God existing, or that the odds are 10% or 90%. The only possibilities are 0% or 100%. Either God's existence is impossible (0%) or it's possible and therefore necessary (100%).

What do you think? Is the modal ontological argument for God a sound proof? If not, how does it fail?

Brandon Vogt

Written by

Brandon Vogt is a bestselling author and the founder of StrangeNotions.com. Brandon has been featured by several media outlets including NPR, CBS, FoxNews, SiriusXM, and EWTN. He converted to Catholicism in 2008, and since then has released ten books, including The Church and New Media (Our Sunday Visitor, 2011), Saints and Social Justice (Our Sunday Visitor, 2014), and Why I Am Catholic (And You Should Be Too) (Ave Maria Press, 2017). He works as the Senior Publishing Director for Bishop Robert Barron's Word on Fire Catholic Ministries. Brandon lives with his wife, Kathleen, and their seven children in Central Florida. Follow him at BrandonVogt.com.

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