Destruction perfects that which is good; for the good cannot appear on account of that which conceals it. The good is least good whilst it is thus concealed. The concealment must be removed so that the good may be able freely to appear in its own brightness. For example, the mountain, the sand, the earth, or the stone in which a metal has grown is such a concealment. Each one of the visible metals is a concealment of the other six metals.