A great religious teacher of the 18th century, Shah Waliullah of Delhi distinguished himself as a major thinker from the age of 15. He helped to revive the Islamic consciousness by "channeling the streams of the Sufi spiritual heritage into traditional Islam" (Professor Aziz Ahmed, Toronto) and returned to the essentials of Sufi experience in order to show that, essentially, Sufism is one discipline. He showed, for instance, that the long-standing assumption that Sufi doctrine was divided between Apparentism and Unity of Being was a difference of expression alone, the latter doctrine (of Ibn Arabi) being seen as merely a less-advanced stage of projection. Many of the subjects dealt with by him in these two treatises are closely studied today. These include stages of being, the perceptive faculty, the relation of the abstract with the universe, the universal soul and the souls of man, after death, essence, miracles, the scope of man, the soul of the perfect, universal order, source of manifestation, and the transformation of mystics from quality to quality.