Recently one question was put to me by an atheist regarding the number of god or gods responsible for creating the universe: ‘You can’t even cite any rational criteria for determining how many gods are responsible. You use the word ‘God’ as if there is only one. What is your evidence that there is only one god?’
So what is my evidence that there is only one God?
I have already shown elsewhere1 that if there is a creator of the universe, then that creator cannot be within any space and time, because logic dictates that a creator will always precede his/her creation. Before creation there was no space and time and therefore the creator god was not within any space and time. That means before creation there was no one else, nothing else other than the creator god, because before creation there was no space and time beyond the creator god within which someone or something might exist. Or, we can also say that before creation there was no one else, nothing else beyond the creator god.
Now instead of calling the creator of the universe as the creator god, we can also call him/her the cause of the universe. Or, in brief, we will call it The Cause. Thus The Cause would be such that before creation there would be no one else, nothing else other than The Cause.
Now let us suppose that there were two gods instead of one: god-A and god-B. Now can we say about god-A that before creation there was no one else, nothing else other than god-A? Can we say about god-B that before creation there was no one else, nothing else other than god-B? No, we cannot say so, because before creation there was already god-B beyond god-A and god-A beyond god-B.
But we have already seen above that before creation there would be no one else, nothing else beyond The Cause, because before creation there would be no space and time. So we see that neither god-A nor god-B fulfils the condition for being The Cause, because The Cause would have to be such that before creation there would be no one else, nothing else other than The Cause. So, either god-A is prior to god-B and is the cause of both god-B and the universe, or god-B is prior to god-A and is the cause of both god-A and the universe. But both of them combined cannot be the cause of the universe.
This clearly shows that there can be only one god, not many.
The whole matter can be analyzed from another angle. The situation before creation would have to be such that there would be no space and time before creation. But if there are two gods, then can we say that before creation there was no space and time? No, we cannot say so, because if there are two gods, then both of them would be within some space and time.
Here we cannot claim that god-A is not within any space and time, This is because if god-A is not really within any space and time, then beyond god–A there would be no space and time within which someone or something might exist and therefore there would be no one else, nothing else beyond god–A. But we already know that there was god-B beyond god-A. That means it cannot be said about god-A that it is not within any space and time.
By the same logic it can be shown that god-B is also within some space and time.
So, if there are more than one gods, then space and time would already be there. That will further mean that creation has already taken place. So, again we will have to say that either god-A is prior to god-B and is the cause of both god-B and the universe, or that god-B is prior to god-A and is the cause of both god-A and the universe. But both of them combined cannot be the cause of the universe.
However it must be mentioned here that it is very much possible that both of them together are not within any space-time. But when we consider them individually and separately, both god-A and god-B would be within some space-time.
Reference:
1. http://www.11prompt.com/?q=node/557#comment-form