RN Dot Tk S 112 AN INTRODUCTION TO SUFI DOCTRINE the soul clings to truth in some revealed form. Virtue is the indirect basis for spiritual concentration, for a vicious soul is not able long to concentrate on truth, and, inversely, spiritual concentration contributes to the developing of virtues. In a certain sense contem- plative virtue cannot become perfected without the help of an inner ‘‘alchemy’ which watches over the trans- mutation of the natural powers of the soul,! but it is through its object, the revealed symbol, that concentra- tion opens the way to the Grace which transforms the soul. The term “alchemy” is very suitable as applied to the art of concentration considered in itself because, from the point of view of this art, the soul is like “‘a matter” which is to be transformed even as in alchemy lead is to be transmuted into gold. In other words the chaotic and opaque soul must become “formed” and crystalline. Here form does not mean a fixation within certain limits but on the contrary a quasi-geometric co-ordination, and hence even a virtuality of deliverance from the limiting conditions of the arbitrary psychic tyranny, just as gold or crystal manifests on the level of solid substances the nature of light, the second both by its geometrical form—the propagation of light being rectilinear—and by its transparence. According to the same symbolism—the nearest to 1. In several respects the Sufi theory of the spiritual virtues differs from that found in the monastic teaching of the Christian Eastern Church. Thus, Sufis do not gencrally look on chastity as a basic virtue but rather as the natural result of the presence of several other virtues.