ʿIlm al-Kalām (Arabic: عِلْم الكَلام, literally "science of discourse"), usually foreshortened to kalam and sometimes called "Islamic scholastic theology", is an Islamic undertaking born out of the need to establish and defend the tenets of Islamic faith against doubters and detractors. A scholar of kalam is referred to as a mutakallim (plural mutakallimūn) as distinguished from philosophers, jurists, and scientists. There are many possible interpretations as to why this discipline was originally called "kalam" (lit. speech); 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.
The Arabic term kalam means "speech" among other things, and its use regarding Islamic theology is derived where the Quran mentions (kalām Allāh) "Word of God".
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".
Even though seeking knowledge in Islam is considered a religious obligation, the study of 'Ilm al-Kalam is considered by Muslim scholars to fall beyond the category of necessity and is usually the preserve of qualified scholars, eliciting limited interest from the masses or common people.
The early Muslim scholar Imam al-Shafi‘i held that there should be a certain number of men trained in kalam to defend and purify the faith, but that it would be a great evil if their arguments should become known to the mass of the people.