Tafsir

Only a Being which has these powers is worthy of being worship لَوْ كَانَ فِيهِمَا آلِهَةٌ إِلَّا اللَّـهُ لَفَسَدَتَا (Had there been gods in them [ the heavens and the earth ] other than Allah, both would have fallen in disorder. - 21:22). This is an argument of common nature in favour of the Oneness of Allah which is based on common practice. It is also a logical proof of the oneness of God and a great deal of literature is available to explain it in the books on theology (عِلمُ الکلَام). The argument of common nature is that if there were two Gods, each independent and sovereign, then the commands of both would prevail on the earth and in the sky which is not possible, because it is inconceivable that both of them would have common views on all matters. And if there are differences of opinion which is inevitable where power is shared, there could be conflict, which would always lead to chaos and confusion. The suggestion that the two Gods could consult each other before passing orders has been adequately discussed, and rejected, in the books of theology.

The thing to note is that if the two Gods had to take decisions jointly, then neither of them would have been sovereign, and a god with divided sovereignty is not God.