And in this manner they interpret every thing, and say that every thing exterior has its interior, which is the cause of the exterior, whilst this latter is the manifestation of the interior; and there is nothing exterior which has not its interior; and if not, there is, in reality, nothing; further, there is nothing interior which has not its exterior, unless it be an illusion. When God created the exterior (visible), and the interior (invisible) world, the latter was the world of spirits, souls, and intelligences; the visible world was that of bodies, upper and nether, and of accidents. The Imám is the lord of the interior world, and there is no knowledge of God to be acquired, except by his instruction. The prophet is the lord of the exterior world, and the law, of which men stand in need, will not be perfect except by him; and the law has an exterior side, which is called _tanzil_,[610] “revelation from heaven, the Koran,” and an interior, which is entitled _táwîl_,[611] “interpretation.” The age is never destitute of a prophet, or of law; it is likewise never without an Imám, or his authority. These sectaries further say, that his government is sometimes concealed, although the Imám be manifest, and that at another time the government is manifest, although the Imám be concealed; in such a manner that the people may know a prophet by the wonders of his words and deeds; but they recognize the Imám by his government and direction, and they cannot know God Almighty but by the Imám. The Shiâhs also maintain that the existence of an Imám through all times is necessary, whether manifest or concealed, so that no period of time be destitute of the splendour of the sun, or plunged in the darkness of night.