Another point of distinction between metaphysics and the empirical sciences is that the latter group proceeds by experimentation or external observation, whereas metaphysics cannot possibly be studied either experimentally or externally. This is why physics, with all its talk, can never approach metaphysical issues in any way other than by analogy, since its method is not capable of grasping anything of the metaphysical order. The limitation has had interesting consequences as physics has continued to develop and has, in some cases, come face to face with metaphysical reality, at which point it breaks down and see only paradox. The prime example of this is the discovery of quantum physics that the act of observation determines the state of that which is observed, but only at a certain level (that is to say, not within everyday experience). Without getting too deep into this problem, we can simply suggest that this great enigmatic discovery, which baffles the physicist, would be seen by the traditional metaphysician as the boundary between determined matter and ‘prime matter’ or materia prima, which is pure potency and thus undetermined until the moment of its ‘actualization’. Thus, the fundamental ‘substance’ that underlies everything else in the universe, that which contemporary physics has so proudly struck upon, but cannot understand, is precisely that which was described by Aquinas, along with its strange behavior, centuries before. For this is precisely what is in question when we speak of ‘wave function collapse’ whereby exposure to the world (the manifest world, that is), or at the moment of observation, that which was undetermined becomes actualized into this thing.