Kant goes into great detail discussing this in
Critique of Pure Reason. A famous quote (although obscure) was his remark: 'Existence is not a predicate' which was in regards to this idea of concept and existence.
What is the difference between a real hundred pounds and an imaginary hundred pounds? A hell of a lot! Now what is difference between them and the
concept of a hundred pounds? None. The concept is the same. In the end Kant argues that existence is not part of concept but something which must be independently validated.
Bertrand Russell also talks about these ideas in "On Denoting". - The
is of existence. He also repeats that 'existence is not a predicate'. Because we can intelligibly talk about things that do not exist it gives the impression they in fact do exist. example:
The king of France does not exist.
Who doens't exist?
The king of France.
this is attributing some sort of existence to the King of France.
Anyway, my point is - its complicated
and more importantly, while the God
concept can exist this doesn't then imply that God exists.
Michael