Moslem thinkers have treated the idea of justice from a religious and human point of view by examining it on two planes: God and Man. Whatever their inclinations may be, their concept of justice is linked to other connected notions such as beauty and ugliness, good and evil, free will, the volition and wisdom of God, and predestination. In the framework of this study of the idea of justice and its related concepts, we shall confine ourselves to setting out the points of view of the principal sects (the Ash'arites, the Mu'tazilites and Maturidism) and of certain philosophers such as Averroes and some mystics including Ibn'Arabi. We shall probably be led to a brief comparison of the ideas of Ibn'Arabi with those of Leibniz. For more ample details on this subject, we refer the reader to a series of articles already published in which we underlined the points of convergence between these two philosophers with regard to the infinite, monadism, optimism, good and evil, and predestination.