What are the conditions of an Islamic state, and what school of thought produced the old Mu'tazilite mentality?

An Islamic state is one that implements Allah's law, establishes justice among people, and enables preachers to enjoin good and forbid evil within it. There are no specific conditions for its establishment; rather, it requires multi-faceted means that vary according to time, place, and people. The available means for most Muslims now are calling to Allah with wisdom and good counsel, spreading Islamic awareness, and clarifying humanity's need for the Islamic religion and an Islamic state that guides to truth and justice.