Monotheism is the essence of Islam. It is the affirmation of believing that there is no other divinity other than God. For the most part, the spirit of the Quran revolves around the theme of pure monotheism. Thus, God is the center of a Muslim’s belief. Whereas other religions focus on individuals, for example, Christianity’s focus on Jesus Christ, Islam focuses solely on God.
Islam is based on the Absolute (God), not His manifestations. The Quran itself speaks about the oneness of God,
“Allah has borne witness that there is no god other than Him, and the angels, and those with knowledge also witness this. He is always standing firm on justice. There is no god but Him, the Mighty, the Wise.” (3:18)
The oneness of God is not only a philosophical argument, rather it is also an affirmation which all human beings once declared before their souls entered their body, as God says,
“[Remember] when your Lord brought forth the children of Adam from their loins and made them testify over themselves, saying, “Am I not your Lord?” They said, “Yes! We testify,” lest you should say on the Day of Resurrection, ‘Verily, we were unaware of this.’” (7:172)
In this event, every person to be created until the end of time proclaimed God’s majesty, sovereignty, power, transcendence, and absolute oneness.
Such was the covenant God made with all people at the time of their creation, whether people presently claim to believe in God or not. Similarly, all people today, regardless of their origin, are naturally inclined towards the idea that God is one and does not have a partner. The Quran informs Prophet Muhammad of the following,
“Set your face to the true religion [the Islamic belief of monotheism], the natural inclination [fitra] with which Allah has created mankind. [Let there be] no change in what Allah has made; that is the straight religion, but most people do not understand.” (30:30)