The second law of thermodynamics states that the amount of energy in a system that is available to do work is decreasing. Entropy increases as available energy decreases. In other words, the purely natural tendency of things is to move toward chaos--not order; and available energy necessary for work is lost (mostly as heat) in this process. Eventually, the universe will run down, and all life and motion will cease because all the energy that exists will be, more or less, evenly distributed so that no work can be performed and no life can exist. This is the natural tendency of all things. Batteries run down, machines break, buildings crumble, roads decay, living things die, etc. Left to the natural state, all things would eventually cease to function.

The universe is not infinitely old because it has not "run down." If the universe were infinitely old, it would have reached a state where all usable energy was gone. But, we are not in this state; therefore, the universe is not infinitely old and must have had a beginning. Because the universe had a beginning, it is not infinite in size. It would require an infinite amount of time to become infinite in size. Since the universe had a beginning, it has not had an infinite amount of time to expand; therefore, it is finite in size. All events have causes. There cannot be an infinite regress of events because that would mean the universe was infinitely old. We've already established that the universe cannot be infinitely old. If it were infinitely old, the universe would be in a state of unusable energy, which it is not. If it were infinitely old, the universe would be infinitely large, which it is not. Since the universe is finite and had a beginning and there cannot be an infinite number of regressions of causes to bring it into existence, there must be a single uncaused cause of the universe. A single uncaused cause of the universe must be greater in size and duration than the universe it has brought into existence. Otherwise, we have the uncaused cause bringing into existence something greater than, or equal to, itself. Any cause that is natural to the universe is part of the universe. An event that is part of the universe cannot cause itself to exist. Therefore, there must be an uncaused cause outside the universe. An uncaused cause cannot be a natural part of the universe, which is finite. An uncaused cause would be infinite in both space and time since it is greater than which it has caused to exist. An uncaused cause would be separate from the universe. Being separate from the universe, which was caused to be, it would not be subject to the laws of the universe since it existed independent of the universe and its laws. This would mean that entropy need not be required of the uncaused cause. This uncaused cause is supernatural. By supernatural, it is meant completely 'other' than the universe and is not the product of it. This uncaused cause must be incredibly powerful to bring the universe into existence. The Bible teaches that God is uncaused, is not part of the universe, created the universe, and is incredibly powerful. God's existence (in Christianity) is not an event but a state. Psalm 90:2 says that God is God without a beginning. This means that God is uncaused. Therefore, the God of the Bible is the uncaused cause of the universe.