Fundamental to the religious structure of Islam is the concept of tawheed, or monotheism. As the seed is to tree, so is tawheed to Islam. Just as the tree is a wonderfully developed extension of the seed, so is the religious system of Islam a multi-faceted expression of a single basic concept. For, monotheism in Islam does not mean simply belief in one God, but in God’s oneness in all respects. No one shares in this oneness of God. Anthropologists would have us believe that the concept of God in religion began with polytheism; that polytheism gradually developed with monotheism. That is, the concept of tawheed was an evolutionary feature of religion which emerged at a later stage. But, according to Islamic belief, the concept of tawheed has existed since the beginning of human life on this earth. The first man—Adam—was the first messenger of God. It was this first messenger who taught human beings the concept of tawheed.
Three Periods of the History of Tauhid