In 1974 Alvin Plantinga developed a modal version of the ontological argument, which is as follows:
- The property of being maximally great is exemplified in some possible world.
- The property of being maximally great is equivalent, by definition, to the property of being maximally excellent in every possible world.
- The property of being maximally excellent entails the properties of omniscience, omnipotence, and moral perfection.
- A universal property is one that is exemplified in every possible world or none.
- Any property that is equivalent to some property that holds in every possible world is a universal property.
- Therefore, there exists a being that is essentially omniscient, omnipotent, and morally perfect (God).
Ax =df x is maximally great
Bx =df x is maximally excellent
W(Y) =df Y is a universal property
Ox =df x is omniscient, omnipotent, and morally perfect
1 ◊(∃x)Ax pr