According to Islamic belief, in addition to sending prophets, God manifests his mercy in the dedication of all creation to the service of humankind. Islamic traditions maintain that God brought the world into being for the benefit of his creatures. His mercy toward humanity is further manifested in the privileged status God gave to humans. According to the Qur'an and later traditions, God appointed humankind as his vice regents (caliphs) on earth, thus entrusting them with the grave responsibility of fulfilling his scheme for creation.

The Islamic concept of a privileged position for humanity departs from the early Jewish and Christian interpretations of the fall from Paradise that underlie the Christian doctrine of original sin. In the biblical account, Adam and Eve fall from Paradise as a result of disobeying God's prohibition, and all of humanity is cast out of Paradise as punishment. Christian theologians developed the doctrine that humankind is born with this sin of their first parents still on their souls, based upon this reading of the story. Christians believe that Jesus Christ came to redeem humans from this original sin so that humankind can return to God at the end of time. In contrast, the Qur'an maintains that after their initial disobedience, Adam and Eve repented and were forgiven by God. Consequently Muslims believe that the descent by Adam and Eve to earth from Paradise was not a fall, but an honor bestowed on them by God. Adam and his progeny were appointed as God's messengers and vice regents, and were entrusted by God with the guardianship of the earth.

The nature of humankind's relationship to God can also be seen clearly by comparing it with that of angels. According to Islamic tradition, angels were created from light. An angel is an immortal being that commits no sins and serves as a guardian, a recorder of deeds, and a link between God and humanity. The angel Gabriel, for example, communicated God's message to the prophet Muhammad. In contrast to humans, angels are incapable of unbelief and, with the exception of Satan, always obey God.

Despite these traits, Islamic doctrine holds that humans are superior to angels. According to Islamic traditions, God entrusted humans and not angels with the guardianship of the earth and commanded the angels to prostrate themselves to Adam. Satan, together with the other angels, questioned God's appointment of fallible humans to the honorable position of viceregency. Being an ardent monotheist, Satan disobeyed God and refused to prostrate himself before anyone but God. For this sin, Satan was doomed to lead human beings astray until the end of the world. According to the Qur'an, God informed the angels that he had endowed humans with a knowledge angels could not acquire.

For centuries Muslim theologians have debated the subjects of justice and mercy as well as God's other attributes. Initially, Islamic theology developed in the context of controversial debates with Christians and Jews. As their articulations of the basic doctrines of Islam became more complex, Muslim theologians soon turned to debating different interpretations of the Qur'an among themselves, developing the foundations of Islamic theology.

Recurring debates among Islamic scholars over the nature of God have continued to refine the Islamic concepts of God's otherness and Islamic monotheism. For example, some theologians interpreted Qur'anic attributions of traits such as hearing and seeing to God metaphorically to avoid comparing God to created beings. Another controversial theological debate focused on the question of free will and predestination. One group of Muslim theologians maintained that because God is just, he creates only good, and therefore only humans can create evil. Otherwise, this group argued, God's punishment of humans would be unjust because he himself created their evil deeds. This particular view was rejected by other Muslim theologians on the grounds that it limits the scope of God's creation, when the Qur'an clearly states that God is the sole creator of everything that exists in the world.

Another controversial issue was the question of whether the Qur'an was eternal or created in time. Theologians who were devoted to the concept of God's oneness maintained that the Qur'an must have been created in time, or else there would be something as eternal as God. This view was rejected by others because the Qur'an, the ultimate authority in Islam, states in many places and in unambiguous terms that it is the eternal word of God.

Many other theological controversies occupied Muslim thinkers for the first few centuries of Islam, but by the 10th century the views of Islamic theologian al-Ashari and his followers, known as Asharites, prevailed and were adopted by most Muslims. The way this school resolved the question of free will was to argue that no human act could occur if God does not will it, and that God's knowledge encompasses all that was, is, or will be. This view also maintains that it is God's will to create the power in humans to make free choices. God is therefore just to hold humans accountable for their actions. The views of al-Ashari and his school gradually became dominant in Sunni, or orthodox, Islam, and they still prevail among most Muslims. The tendency of the Sunnis, however, has been to tolerate and accommodate minor differences of opinion and to emphasize the consensus of the community in matters of doctrine.

As is the case with any religious group, ordinary Muslims have not always been concerned with detailed theological controversies. For ordinary Muslims the central belief of Islam is in the oneness of God and in his prophets and messengers, culminating in Muhammad. Thus Muslims believe in the scriptures that God sent through these messengers, particularly the truth and content of the Qur'an. Whatever their specific religious practices, most Muslims believe in angels, the Day of Judgment, heaven, paradise, and hell.