The Ontological Argument for the existence of God has been loved and hated by both philosophers and theologians alike since its original formation by Saint Anselm in 1078 AD.  It was revised by German philosopher and mathematician Gottfried Leibniz, and it was on his version logician and mathematician Kurt Godel based his mathematical formula of this argument (which has been computer verified.) More recently American philosopher Alvin Plantinga produced a modal version of this argument which is the bases for the argument listed below. 

The word ontological means “being” or “the nature of being”.  Modal logic is a formal system represented in statements about necessity and possibility. 

Anselm, as well as those who developed this argument, thought of God as “a maximally great being of whom none could be greater.” Maximal greatness means holding properties of greatness (all loving, all caring, all powerful, all knowing, etc). Plantinga draws a distention between maximal greatness and exceptional greatness (an exceptionally great being is possible but not necessary, while a maximally great being would not only be possible but is also necessary.)  If you are new to philosophy your head might be spinning.  Think of it as a gas tank that is so full that you can’t add any more to it, but instead of gas it is full of everything good and can never run out.

The argument speaks of “possible worlds.”  In philosophy a possible world is the way things might be or could be (it is not physical planets or the multiverse, but rather possibilities).  Think of the movie Back To The Future.  In the original film we are presented with three possible worlds.  The first one we see Marty living a fairly normal life – but he has self doubt, his mother is unhappy, and his father George is unsuccessful.  When he travels back in time he changes things which causes his brother and sister to dissolve out of existence – even Marty starts to dissolve because his mother and father never get together. This would be possible world two.  The third possible world is that to which Marty returns.  Because George clocked Biff when Marty returns his family has changed.  His brother and sister are productive, his mom and dad are happy, and his father is a success (not to mention that Biff now works for George).

With this foundation, let’s look at Plantinga’s Ontological Argument.

1. It is possible that a maximally great being exists.

2. If it is possible that a maximally great being exists, then a maximally great being exists in some possible world.

3. If a maximally great being exists in some possible world, then it exists in every possible world.

4. If a maximally great being exists in every possible world, then it exists in the actual world.

5. If a maximally great being exists in the actual world, then a maximally great being exists.

6. Therefore, a maximally great being exists.

This is a logically air tight argument.  In order for it not to be true one of the first five premises must be false.  If premises 1-5 are true then the conclusion must be true.

Some have tried to argue against this using a parody.  Gaunilo of Marmoutiers, an 11th century Benedictine monk, argued against Anselm’s original ontological argument stating that there could be a mythical lost island that is the greatest island ever.  But these only work against Anselm’s construction of the argument which dealt with what could be conceived as great is better in reality than in thought (i.e. thinking about having a million dollars is different than actually having a million dollars).  Contingent things, such as islands, can always have something added to it to increase its greatness – or one person’s ideal island may not be another person’s ideal island.  So these arguments do not work against a modal construction of the argument where possibility and necessity are used.

I like this argument for three reasons.  1. It appeals to my sense of metaphysics.  2. It provides a platform by which the existence or non-existence of God can be discussed.  For the theists then, he or she would need to show that the existence of God is possible.  This can be done through various arguments from natural theology such as from contingency (or other cosmological arguments), or objective moral values and duties. Or, for that matter, from theological arguments and evidences.  The point being if God is possible then God exists.  The atheist, on the other hand, has to demonstrate that God’s existence is impossible in order for the argument not to work. 3. It presents God as He has revealed Himself through Scripture and nature, namely He who is maximally great.  And once we grasp, at least as much as we can grasp the greatness of God, this argument is self-evident.  Regardless, it is not to be taken lightly and is a philosophically strong argument for God’s existence.

“For My thoughts are not your thoughts, 
Nor are your ways My ways,” declares Yahweh. 
“For as the heavens are higher than the earth, 
So are My ways higher than your ways 
And My thoughts than your thoughts.” (Isaiah 55:8-9 LSB)

“Oh, the depth of the riches both of the wisdom and the knowledge of God! 
How unsearchable His judgments and untraceable His ways!” (Romans 11:33 LSB)