16mo, softcover wrappers, 112pp. First pocket edition of the original 1938 text by Burns Oates. Wrappers mildly worn to edges. Contents clean, binding crisp and firm. ‘A brief outline of the main principles of ascetic and mystical theology.’ The celebrated treatise on the three conversions (purgative, illuminative, unitive) by the French Dominican theologian, a brief outline of his much longer work “The Three Ages of the Interior Life.” Out of print and scarce. A nearly fine copy.