This article deals with the discussion of causality among the Mutazilite scholars. First and foremost we have tried to explain the background of this argument. Altough we cannot disregard the external influence, it is important to note that the discussion begins with the analysis of the relationship between the notion of God’s ultimate power to do everything and cause-effect in outside world. The Mu’tazilite branches of Basra and Baghdad schools display different approaches to solve this problem. Baghdad school places great stress on the role of nature though they believe that God has power to do everything. Basra school of thought accepts the causality theory, however, they claim that it is not necessary to find its application in everything. In order to understand both schools’ causiality discussion we fo-cus on the most important representatives of both schools, namely Ibrahim al-Nazzam from Basra and Abu al-Qasim al-Ka’bi from Baghdad.