There are but a few persons who imitate the Sufis in this practice of self-examination, for negligence and indifference in this respect are almost universal. Pious men who have not risen to this class (the mystics) only aim at fulfilling the works commanded by the law in all the completeness laid down by the science of jurisprudence. But the mystics examine scrupulously the results of these works, the effects and impressions which they produce upon the soul. For this purpose they use whatever rays of divine illumination may have reached them while in a state of ecstacy, with the object of assuring themselves whether their actions are exempt or not from some defect. The essence of their system is this practice of obliging the soul often to render an account of its actions and of what it has left undone. It also consists in the development of those gifts of discrimination and ecstacy which are born out of struggles with natural inclinations, and which then become for the disciple stations of progress. The Sufis possess some rules of conduct peculiar to themselves, and make use of certain technical expressions. Of these Ghazzali has treated in _Ihya-ul-ulum_ ("Revival of the Religious Sciences"). He speaks of the laws regulating devotion, he explains the rules and customs of the Sufis and the technical terms which they use. Thus the system of the Sufis, which was at first only a special way of carrying on worship, and the laws of which were only handed on by example and tradition, was methodised and reduced to writing, like the exegesis of the Koran, the Traditions, Jurisprudence, and so forth. This spiritual combat and this habit of meditation are usually followed by a lifting of the veils of sense, and by the perception of certain worlds which form part of the "things of God" (knowledge of which He has reserved for Himself). The sensual man can have no perception of such things. Disentanglement from the things of sense and consequent perception of invisible things takes place when the spirit, giving up the uses of exterior senses, only uses interior ones; in this state the emotions proceeding from the former grow feebler, while those which proceed from the spirit grow stronger; the spirit dominates, and its vigour is renewed. Now, the practice of meditation contributes materially to this result. It is the nourishment by which the spirit grows. Such growth continues till what was the knowledge of One absent becomes the consciousness of One present, and the veils of sense being lifted, the soul enjoys the fullness of the faculties which belong to it in virtue of its essence, _i.e._, perception. On this plane it becomes capable of receiving divine grace and knowledge granted by the Deity. Finally its nature as regards the real knowledge of things as they are, approaches the loftiest heaven of angelic beings.