Perhaps no argument is more complicated than the ontological argument when discussing the evidence for God. Many will feel like this one is a trick. But the logical structure is sound, and if the premises are true, the conclusion necessarily follows. If this evidence becomes too difficult to process, continue to the next section. That one will be easier and may enhance your understanding of this one. When one grasps this argument, however, disbelief in God is revealed as ignorance of who He truly is.
The argument was first developed by Anselm of Canterbury in the 11th century. Anselm argued that the existence of God was not only likely, but necessary, and Psalm 14:1 says it’s foolish to claim there is no God.
Here are the premises of his argument and his conclusion:
Premise 1: God is the object of thought of which no object of thought can be considered to be greater.
Now suppose God is only in the intellect (i.e., He exists in the mind but not in reality). But…
Premise 2: Any object of thought that can be believed to exist in reality will certainly be thought to be greater than any object of thought that exists only in the intellect.
Premise 3: It cannot be doubted that God can be thought to exist in reality, not only in the intellect.
Premise 4 and Conclusion: Therefore, some object of thought can be thought to be greater than the object of thought of which no object of thought can be greater, which is a contradiction. And so, we have to abandon our supposition that God is only in the intellect. He must also exist in reality.
Anselm argues God is not simply a being that might exist, but rather by definition, is a being that must exist – He is a necessary being. Instead of going into detail defending each premise, which isn’t difficult, we will first look at a modern-day construction of the argument by philosopher Alvin Plantinga.
Before listing the premises and conclusion, let me clarify a few terms. When philosophers speak of “possible worlds”, they simply mean a way that reality could be, not necessarily the way reality is. For example, unicorns don’t exist, but there is a possible world where they do exist. This means we can imagine a logical world where unicorns are a creature, even if they’re not a creature in the real world.
Not every world is possible, though. There is no world where square triangles exist because that is logically and mathematically impossible. A world with black and white rainbows isn’t possible either, because rainbows are, by definition, related to the visible spectrum of light. A possible world is a valid description of how the world could logically be.
Next, Plantinga uses the phrase “maximally great being”. A maximally great being is infinite in power and knowledge, is omni (all) benevolent (good), and is eternal in nature (not bound by time).
Keeping these two concepts in mind, here is Alvin Plantinga’s structure for the ontological argument:
Premise 1: It is possible that a maximally great being exists.
Premise 2: If it’s possible that a maximally great being exists, then a maximally great being exists in some possible world.
Premise 3: If a maximally great being exists in some possible world, then it exists in all possible worlds.
Premise 4: If a maximally great being exists in all possible worlds, then it exists in the actual world.
Premise 5: Therefore, a maximally great being exists in the actual world.
Conclusion: Therefore, God, the maximal being, exists.
It may surprise you that Premises 2 – 5 are fairly noncontroversial. Logically they must be true. The debate is with Premise 1 and whether it’s possible for God to exist in some world. The atheist must argue that it’s logically impossible for God to exist in any world, just as it’s impossible for square triangles to exist. If it’s possible that God exists in any world, He must exist in the actual world, which concludes that God exists.
Why, though? Why does this maximally great being have to exist in all worlds? Simple! A maximally great being can’t be confined to one world; by definition, maximal greatness would be maximally great in all worlds.
Atheists try to parody this argument in order to manipulate it as a trick that is not logically sound, but their attempts constantly fall short. Atheist philosophers will say, “Imagine a great island, the greatest island possible, therefore the island exists!” Initially, people might think there is weight to this argument, but it’s quite inconsistent. Any parody uses the natural material world to make the parody – an island, for example. But maximal greatness can’t be constrained to the world or nature, because one could always add another palm tree or hula dance to the island in order to make it better. The only way to get maximal greatness is a timeless, infinite, personal being (maximal greatness must be linked to goodness and personhood), and God is the only option.
Finally, there is only one possible maximally great being, because maximal greatness includes infinite power and control, which can only be held by one maximally great being. Two beings cannot each possess infinite power. Two cannot be in control of all things, so there can only be one God – one maximally great being.
If you struggled with understanding this argument, try re-reading the section, or progress to the next one. If it made sense to you, I hope you see how God is not only possible, but indeed a necessary being. If it’s even possible God could exist, He does.