How does the ontological argument support the existence of God?

TL;DR:

The ontological argument suggests that if it's even possible for God to exist, then He must exist logically. This argument is based on the idea that the concept of a maximally great being, or God, necessitates His existence in all possible worlds, including our own.

what does the bible say?

Ontology is the philosophical study of being. The ontological argument to support the existence of God, the supreme being, originated with Thomas Anselm in the 11th century. While details of the argument have been modified since then, the basic argument can be stated as follows: if it is even possible that God exists, then it follows logically that God does exist. The Bible assumes the existence of God starting with the first verse, "In the beginning God created the heavens and the earth" (Genesis 1:1). The Bible does not present arguments for the existence of God because His existence is plain for everyone to see (Psalm 19:1; Romans 1:20). Outside the Bible, many logical, philosophical, and scientific arguments have been developed to prove God's existence, including the ontological argument.

from the old testament

The design and order of the natural world reveals the existence of God and His attributes (Psalm 19:1).

from the new testament

God has made His existence plain for everyone to see. His eternal power and divine nature are clearly perceived from creation (Romans 1:19-20).
We are to know what we believe and why. At the same time, our heart attitudes in the way we communicate what we believe matters: "...in your hearts honor Christ the Lord as holy, always being prepared to make a defense to anyone who asks you for a reason for the hope that is in you; yet do it with gentleness and respect" (1 Peter 3:15).

implications for today

The most popular modern expression of this argument was published by Alvin Plantinga and popularized by William Lane Craig as follows:

Begin by noting that it is logically possible for there to be a greatest conceivable being (or “maximally great” being), which is what we mean by God. If that is true, then there is at least one logically possible world in which the greatest conceivable being existed. But, by definition, the maximally great being must exist in all possible worlds, or he would not be maximally great. Therefore, since he does exist in a possible world, by definition he exists in every possible world, which means he exists in the real world. In other words, unless the concept of God is completely incoherent, God logically must exist.

If you get the feeling that the argument is playing some kind of trick on you, you are not alone: many find the argument unpersuasive and unhelpful. However, when the argument is formulated carefully, it turns out to be a deductively valid argument which hinges only on the assumption that it is possible that God exists. That is a reasonable assumption, and the rest of the argument follows logically.

Unlike many arguments, the ontological argument argues from God rather than to Him. It is rooted in the very nature of God and is therefore specific to the true and living God. It does not present God as something that might or might not exist and that we need to prove one way or the other but rather insists that He must exist. This argument takes the person out of the position of judging what is true and places them in the position of responding to the truth (1 Peter 3:15).

understand

The ontological argument states that if God’s existence is possible, He must exist logically.
The Bible assumes God's existence as evident in creation.
The ontological argument emphasizes that the concept of a maximally great being requires existence in all possible worlds.

reflect

How do you understand and apply the ontological argument of the existence of God
How does the idea of a "maximally great being" challenge or strengthen your understanding of God's nature?
What role does the natural world play in how you perceive God's existence?

engage

How can we effectively use the ontological argument in conversations with someone who may be skeptical of God’s existence?
How does the ontological argument align with or differ from the biblical teaching of God’s clear revelation in creation (Romans 1:19-20)?
How does the ontological argument challenge or support the way we think about the relationship between faith and reason?