Murtada Mutahhari describes Kalām as a discipline devoted to discuss "the fundamental Islamic beliefs and doctrines which are necessary for a Muslim to believe in. It explains them, argues about them, and defends them" (see also Five Pillars of Islam). There are many possible interpretations as to why this discipline was originally called so; one is that the widest controversy in this discipline has been about whether the "Word of God", as revealed in the Qur'an, can be considered part of God's essence and therefore not created, or whether it was made into words in the normal sense of speech, and is therefore created.
As early as in the times of the Abbasid Caliphate (750–1258 CE), the discipline of Kalam arose in an "attempt to grapple" with several "complex problems" early in the history of Islam, according to historian Majid Fakhry. One was how to rebut arguments "leveled at Islam by pagans, Christians and Jews". Another was how to deal with (what some saw as the conflict between) the predestination of sinners to hell on the one hand and "divine justice" on the other, (some asserting that to be punished for what is beyond someone's control is unjust). Also Kalam sought to make "a systematic attempt to bring the conflict in data of revelation (in the Qur'an and the Traditions) into some internal harmony".
Historian Daniel W. Brown describes Ahl al-Kalam as one three main groups in the time around the second century of Islam (Ahl ar-Ra'y and Ahl al-Hadith being the other two) clashing in polemical disputes over sources of authority in Islamic law. Ahl al-Kalam agreed with Ahl al-Hadith that the example of the Muhammad, the prophet of Islam, was authoritative, but it rejected the authority of ahadith on the grounds that its corpus was "fill with contradictory, blasphemous, and absurd" reports, and that in jurisprudence, even the smallest doubt about a source was too much. Thus, they believed, the true legacy of the prophet was to be found elsewhere. Ahl al-Hadith prevailed over the Ahl al-Kalam and most of what is known about their arguments comes from the writings of their opponents, such as Imam al-Shafi'i.