The ontological argument is a conductive argument. It is not based on observation of the world but rather on reason alone.

There is no need for physical evidence of God’s existence; we can work out that he exists just by thinking about it.

 

Here is the argument in its logical state:

1. God is the greatest being or greatest thing we can imagine.

2. Things can exist only in our imagination, or they can also exist in reality.

3. Things that exist in reality are always better than things that exist only in our imagination.

4. If God existed only in our imagination, he would not be the greatest thing that we can think of, because God in reality would

     be better.

5. Therefore, God must exist in reality.

The Ontological Argument's main flaws:

1- God's essence cannot be known – this means that we cannot say that God is a being for which no greater being can be thought of.

2- We can use the assumed argument to prove that anything we imagine could exist in reality and this can not hold true. It is just absurd to prove  the existence of a perfect being by simply imaging it.

 

This argument has further serious objections and many philosophers have considered this argument to be absurd.

The Ontological Argument

Note:

In my book 'The Islam Delusion - Volume 1 , Chapter 6' I have discussed to a great length and in a simplified manner all the main evidence available so  far to prove God's existence. I have also addressed other claims of God's existence such as gut feelings, and hearing godly voices. All have been refuted in a professional manner with clear evidence based on reason and common sense.