Metaphysics is discourse on being and so on what cannot not be. But then <pound the table> what about this? This is being, and it obviously can cease to exist and almost certainly will. So what about the contingent?
First, I want to lay aside a dead-end attempt to solve the problem by pointing to the difference between being and a being, or being and its instantiations. When we say being cannot not be this is not because we are considering it as an abstraction. If this is all we meant, being would be no more interesting or problematic than “cat”, since taken as an abstraction and not as a cat, it also doesn’t share in the contingency of a particular instance. But for being not to be is an unintelligible as a cat not to be feline, which applies as much to the concrete case as in the abstraction. If being is anything at all even in the concrete instance it is immediately everlasting. So we are left again pounding the table and asking “So what is this then?”
1.) The Parmenidean. We owe the discovery that being cannot not be to Parmenides, who in turn gave one of the two simplest answers to the problem: If being cannot not be then the world given by the senses does not exist. Sense intuition gives us only doxa or subjectively conditioned information, and discourse about the sensible never rises above opinion, i.e. an opinion that could easily be overturned by later evidence.
2.) The Kantian. Kant implicitly agrees with Parmenides that if being is true and real then the information proceeding from sense intuition cannot be, but Kant bases all knowledge on such intuitions and claims that being is a rational or logical concept as opposed to a reality that is seen in the world. If it is true that “cat” and “being” differ so radically, this is because the first is real while the other is an abstraction from the real.
While Kant was not an analytic philosopher his account of being is the inspiration for the dismissive or “thin” accounts of being that characterize that tradition (with the notable exceptions of BV, Milton Munitz and Barry Miller). The trivialization of existence that one finds in the Analytic tradition – the shepherd going out in the morning to count his non-existent sheep or existence as little more than a comment about the number of things one has – is the mirror image of the Parmenidean trivialization of natural science. Metaphysics is not about anything, but only a gesture in the direction of things we should get to know by physical science and (maybe) moral theory.
3.) Triangulation theories. The Parmenidean and Kantian-Analytical traditions mark out the two extremes of the question of being by making it either real to the exclusion of the contingent-sensible or a purely logical predicate. Most theories try to triangulate these two extremes by carving out some sort of reality for being and the contingent.
a.) Participation theories. In one sense every triangulation theory is a participation theory. More narrowly, we’re talking about the Platonic theory that sees contingent reality as an accident of an eternal form projected onto a receptacle. As an accident, it has the power to remind us of a the form that we have already known in some prior way, but the things of the physical world are not substantial. Aristotle’s linguistic account of substance as what is not predicated of or present in another does not target any ontological reality but is only a linguistic description of things that are insubstantial in themselves.
b.) Complex-substance theories. Here having a form is seen as making things substantial, though they are still derivative entities to things that are purely formal. The substantial entities depend on the purely formal ones in either the order of agent or final causality, and therefore as upon a purely extrinsic cause. While these theories preserve our intuitive sense of the substantiality of the world, they make it dependent on purely formal being only in the order of generation. Once a substance is generated, it is as substantial as purely formal being.
c.) Creation theories. The things of the world are substantial, but this substance has an intrinsic dependence on an extrinsic, purely formal reality. This occurs because this purely formal reality is responsible not only for the generation of the substance but for its act of existence. All natural generation therefore converges on a formality that it is incapable of achieving of itself, even though it is the fulfillment of the very process of generation.