(ii.) The Sufi doctrine of God as the only reality has a direct bearing not only on creation but also on the problem of good and evil. As a thing can only be known by its opposite, light by darkness, health by sickness, being by non-being, so God could only be made known to man as reality contrasted with non-reality, and the mingling of these two opposites produces the world of phenomena in which light is made known by a background of darkness, which darkness is itself only the absence of light: or, as being proceeds by successive emanations from the First Cause, and becomes weaker or less real in each emanation as it recedes further from the great Reality, it incidentally becomes more perceptible as it becomes less real. Thus evil, which is merely the negation of the moral beauty of the Reality, appears in the latest emanation as the unreal background which is the inevitable result of a projection of the emanation from the First Cause, who is entirely good, into a world of phenomena. Evil is therefore not real, it is merely the result, the inevitable result, of the mingling of reality with unreality. In fact, this is implied in the doctrine that all other than God is unreal. (iii.) The aim of the soul is union with God. This doctrine of _tawhid_, as we have seen, received early expression in Muslim mystic theology. Dr. Nicholson is of opinion that “the Sufi conception of the passing away (_fana_) of individual self in universal being is certainly of Indian origin. Its first great exponent was the Persian mystic Bāyazīd of Bistām, who may have received it of his teacher, Abū `Alī of Sind (Scinde.)” (Nicholson: _Mystics of Islam_, p. 17.) But this is only one particular way of presenting a doctrine which has a much wider range and is present in all mystical teaching, including that of the neo-Platonists. In the highest sense it is the basis of Sufi ethics, for the _summum bonum_ is defined as the union of the individual soul with God, and all is good which helps towards this, all is evil which retards it, and this is true of Christian and all other forms of mysticism equally. We cannot say definitely that the doctrine of the unitive state is borrowed from neo-Platonism, from Buddhism, or from Gnosticism; it is the common property of all, and is the natural conclusion from the mystics premises as to the nature of God and of the human soul. It may well be that certain presentations of this doctrine show Indian details, but in this as in all other parts of Sufi speculation it seems that the constructive theory employed in forming a theological system was neo-Platonic: even in mysticism the Greek mind exercised its influence in analysing and constructing hypotheses.