[20] But we must place those arguments first which make out the world to be uncreated and indestructible, because of our respect for that which is visible, employing an appropriate commencement. To all things which are liable to destruction there are two causes of that destruction, one being internal and the other external; therefore you may find iron, and brass, and all other substances of that kind destroyed by themselves when rust, like a creeping disease, overruns and devours them; and by external causes when, if a house or a city is burnt, they also are consumed in the conflagration, being melted by the violent impetuosity of the fire. A similar end also befalls animals, partly when they are sick of diseases arising internally, and partly when they are destroyed by external causes, being sacrificed, or stoned, or burnt, or when they endure an unclean death by hanging.