Since a human being does not have all of these divine attributes, he cannot comprehend the nature of the God simply by thinking about Him. Since human beings are also different, their opinions on the nature of God will also be different as history attests.
As God in the Qur’an explains,
He [God] knows what is happens to them in this world and what will happen to them, but they will never compass anything of His Knowledge.
Therefore, the only way for human beings to know God is for God Himself to reveal His Nature.
Muslims believe this divine revelation to be the Qur’an. On the basis that the Qur’an is indeed the Speech of God, God must therefore be One because He says so in the Qur’an:
Say, ‘He is Allah (swt) [God], [the] One.’
God is the Uncaused Cause of the universe and is personal with a will. Therefore, God must be able to impose His Will independently of all causes.
If, say, two personal gods exist and one wishes to create the universe but the other does not, then:
- either one god wins and the other does not
- neither win
- both win
The second possibility cannot be true because this would mean the universe is neither created nor uncreated, and this is a logical impossibility.
The third possibility cannot similarly be true because the universe cannot be created and uncreated, and this is again is a logical impossibility.
In the first possibility, the one god who can impose his will must be God because He is the Cause of the universe and He is the First Cause, whereas the other god is not the First Cause and cannot prevent God from causing something. Therefore logically God can only be One because only One God can impose His Will independently of all other gods, of all causes. Only One God can, therefore, be the Cause of the universe.