A seventh argument, closely related to some of the others, is drawn from the old belief in the earth as the centre of gravity, the heaviest body in the universe, and in the empyrean as the outermost limit and the lightest body.[312] But, as we have seen, there is in the universe no centre--as the stars and their inhabitants are heavenly beings to us, so are we and our earth to them. "Just as the earth knows no centre or downward direction proper which is away from its own body, but only a centre of its mass, a central cavern of its heart, from which the precious life is diffused through the whole body, and which we may believe to be the chief seat of the soul; so there must be in the moon and other bodies a centre which connects all parts, to which every member contributes, and which is nourished by all the forces of the living body." The old belief, therefore, that if there were inhabitants at the antipodes they would be apt to fall downwards into space, or that the parts of the moon and its living beings might fall upon our earth, was absurd, for the face of the earth always looks upward in the direction of the radii from the centre to the superficies.[313] [Sidenote: 8. The perfect as the self-limited.] The last argument was that drawn from the supposed perfection of the universe.[314] Aristotle defined the perfect as that which was limited by itself, not by another. Hence the immeasurable would not be perfect, while the world was perfect because limited by its own terminus. Again body does not pass over into any other kind of quantity, but it is the limit into which the line and the point flow. The first argument, said Bruno, would hold of any fragment of body, while the second would apply to any animal or member of an animal, for these also are self-contained and do not pass over into any other kind. Perfection has no reference to quantity, nor to limitation by self, which is a geometrical determination.[315] For this mechanical idea of perfection, Bruno substitutes a teleological; the perfect is that which consists of a number of parts or members, working together towards the end for which the whole is ordained: the universe is perfect "as adorned by so many worlds, which are so many deities, and as that in and to which, as a unity embracing the perfection of all, innumerable things perfect in their kind are reduced, referred, united."[316] [Sidenote: Infinite number of worlds.]