METAPHYSICS A lithograph of F Stassen illustrates the moment in Wagner’s opera in which Isolde hands the fateful potion to Tristan arrival at the terminus will be exhibited as some kind of good for the agent whose activity is to be explained Thus, the downward motion of heavy bodies on earth was explained by Aristotle as a movement towards their natural place, the place where it was best for them to be, and the circular motion of the heavens was to be explained by love of a supreme being Similarly, teleological explanation of the development of organic structures showed how the organ, in its perfected state, conferred a benefit 175