I accept that some sort of “Higher Being” created the universe. But why couldn’t there be many such beings? Is there any logical reason to say that there is only one god?
The definition of G‑d is: “a Being without definition.” G‑d cannot be defined, because if I define Him then I limit Him. And something limited is not G‑d. By defining something, I give it borders. If, for example, I define an apple as a sweet round fruit that is green or red, then when I find a long purple fruit, I know that it can’t be an apple. An apple is limited to being round and red or green. That is its definition. G‑d can’t be defined, because by defining Him you are saying that there’s something He can’t be; but this could not be true, because G‑d is unlimited.
That’s why there can be only one G‑d. Because if you don’t have a definition, then there is nothing outside of you. There can be no “other.”
An example: two neighboring countries can be called two countries only when there is a border between them. But if a country has no borders, if there is no defined place where it ends and another country begins, how can you say that there are two countries?
G‑d has no borders, so how can there be more than one god? Where would one god end and one begin, if there is no dividing line between them?
The act of creation is the act of making borders and drawing definitions: this is an apple and not a banana, this is land and this is sea. Creation has definitions. The Creator doesn’t have a definition. That’s what makes Him G‑d. And that’s why there can be only one.