In metaphysics, the notion of contingent and non contingent being often comes up. A thing or object that is contingent, is something that has the potential to fail to exist. It's very existence is contingent upon something else, with a good example being the planet earth. The earth is contingent upon an exploding star and the right gravitational circumstances to allow for it's formation. Something non contingent is something that cannot fail to exist, and does not owe it's existence to anything else. This whole issue of contingency is the basis of a popular argument for the existence of God. I cannot recall who first presented this, but it has appeared in various forms ever since. It goes like this: P1: The physical universe is made up of contingent parts P2: Since these contingent parts will eventually fail to exist, given enough time the universe as a whole should fail to exist. P3: The physical universe exists. Conclusion: Thus, something non contingent exists which created the physical (and contingent) universe. We will call this non contingent being God. This is an interesting argument, because everything we know in the universe does in fact appear to be contingent upon something else. Although this was used as an argument for God, it is really only an argument for non contingent being, since calling non contingent being God is quite arbitrary. So the question is, does the argument have validity? One attempt to answer the question is to deny the first premise that everything in the physical universe is contingent. Perhaps the atoms that make eveything up are contingent, but what about fundemental particles themselves? This was the classic atomist view of eternal particles. But modern physics has overturned this view. Take any fundemental particle, such as a photon. Far from being non contingent, a photon can be obsorbed by another particle, causing a jump in it's energy level. The photon has ceased to exist. So particles are out. But what about the fact the energy in the universe is conserved? If the universe is seen as ever transforming forms of energy, would that not mean the universe as a whole is non contingent? It would seem not. The problem is that a universe in one form is not equivalent to another. For example, we can imagine the universe as an expanding one dimensional piece of string, and view the different shapes the string can take as different forms of energy. What then? The problem is that we cannot define the term universe precisely enough with this definition. A piece of string with x length is not the same as string with y length, and strings with different geometries are not equivalennt. So when we're taking about any precise definition of the universe, the physical world is indeed contingent. Any possible state the universe can take will fail to exist. That seems to be a result of change, since change is the reason any given state fails to exist in the first place. The only possible non contingent being would be one that does not change. So does the arguement for non contingent being, or in the case of theologians, God, hold? I would argue it doesn't. The argument hinges on what it means for something to fail to exist. In the physical world, it's change that brings this about. But a physical object never vanishes into thin air, as it is transformed into something else. If we look at the universe as a whole, any given state will fail to exist, but only by transforming into a new state. So with the premise that an object failing to exist leaves another in it's place, the argument that the physical universe should not exist no longer follows. So it is logically consistent to claim the physical world is an endless chain of events, given that nothing ever vanishes by itself. Ultimately, I think the only other option (to propose the existence of something timeless) fails because it runs into a logical contradiction. Something timeless cannot create anything, by definition. There is also the idea that all of time exists as a static 4 dimensional universe, but that idea seems like an easy way out.