Plantinga's Ontological Argument

Alvin Plantinga wrote his Ontological Argument from a background of logic and mathematics and wrote it in the form of a modal argument. Modality refers to the statement’s necessity, possibility or impossibility. For example, is the statement “God exists” necessary, possible or impossible? Plantinga’s argument outlines the concept of possible worlds. A possible world is a complete way that things can be, meaning there is an infinite number of possible worlds for every possible difference in these worlds. For example, a necessary truth is one that is true in every possible world, and a contingent truth is true in some worlds but not others and an impossible truth is one that is untrue in every possible world. Plantinga criticizes Malcolm for unsuccessfully demonstrating God’s existence in all the possible worlds, saying he merely demonstrated the potential of God’s existence in some possible worlds.

Plantinga’s argument goes as follows:

1. There is a possible world W in which there exists a being of maximal greatness.
2. A being of maximal greatness would possess this quality in all possible worlds.
3. A being of maximal greatness is omniscient, omnipotent and has moral perfection in every possible world.
4. In world W there exists a being which is omniscient, omnipotent and has moral perfection.
5. In world W, the proposition “there is no omniscient, omnipotent and morally perfect being” is impossible.
6. What is impossible in one world is impossible in every possible world.
7. This means the proposition “there is no omniscient, omnipotent and morally perfect being” is impossible in the actual world.
8. Therefore, it is necessarily true that an omniscient, omnipotent and morally perfect being exists in every possible world, including the actual world.

Norman Malcolm - Ontological Argument

Norman Malcolm was a 20^th Century philosopher, and his ontological argument focused on the premise of Anselm’s second argument that God exists necessarily.

Malcolm’s argument goes as follows:

1. If  God does not exist, his existence is impossible
2. If God does exist, his existence is necessary
3. God’s existence is either impossible or necessary
4. God’s existence is not impossible
5. Therefore, God exists necessarily

Malcolm implicitly defines God as immutable (possible point of criticism as he is making an assumption), meaning he is unchangeable. In terms of the argument, this means that God would not change from non-existence to existence as it is impossible, so God’s existence is either necessarily true or necessarily false (see below).

Malcolm outlines four possibilities about God’s existence:

1. Necessarily false - God can’t exist
2. Contingently false – God could but doesn’t exist
3. Contingently true – God could and does exist
4. Necessarily false – God has to exist

Malcolm argues that the existence of an unlimited being is only logically impossible if the concept of an unlimited being is contradictory. “The square is round” for example, is logically absurd and contradictory, whereas the statement “God exists” is not impossible in the same way, so is not a contradiction. Therefore, it is not valid to say that God’s existence is impossible, so he must exist necessarily.