Can we prove that God exists? We cannot prove scientifically that God exists but neither can we prove that He does not exist. Since God is supernatural, He cannot be proven to exist through natural methods. While we cannot prove through the scientific method that God exists, we can show through arguments based on logic and other proofs that there are excellent reasons to believe God exists.
The Cosmological Argument consists of three basic parts. Whatever begins to exist had a cause. The universe began to exist. Therefore, the universe had a cause.
First, does everything that exist have a cause? For something to not have a cause, it would need to be eternal or self-caused. We can say that with confidence based on prior evidence and experience as well as the laws of logic.
Second, did the universe have a cause? There are some that would claim that the universe is eternal or that it was self-caused, but there are several reasons to believe that the universe had a cause outside itself. The universe is expanding, which indicates that it was not always like it is today. Most scientists believe that this expansion was a direct result of the Big Bang. The Big Bang was that moment when space and time came into existence from non-existence. The Big Bang, like a stick of dynamite in a watermelon, exploded the contents of the universe outward. One of the discoveries that helped in cementing the theory of the Big Bang was the discovery of background radiation that would have been left over from the initial explosion.
In addition to the evidence for the Big Bang theory, one of the fundamental laws of nature, the Second Law of Thermodynamics, states that all available energy in a closed system will slowly be used up in a process called entropy. The First Law of Thermodynamics states that there is a finite amount of energy in any closed system. If the amount of energy is less than the energy previously available that means that the system is dying. Now, because nothing eternal, by its very nature, can end, then we can say that the universe, because it is now dying, once had a beginning.
Of course, there are those who proposed an alternative theory to the universe that would allow for its eternality. The first theory, the Steady State Theory, proposes that as the matter in the universe is spread farther apart, new matter appears in the now open spaces. Of course, that begs the question of just what is creating the new matter. The second theory, The Oscillating Universe Theory proposes that the universe is like a giant Slinky. Once it expands far enough, it will begin to contract until it contracts back into a small ball of furious energy, where it will then explode and start the process all over again. Of course, this theory also runs contrary to the First and Second Laws of Thermodynamics as well as any obvious evidence. Like the dynamite in a watermelon, the pieces aren’t pushed far by the explosion only to contract when they reach a certain length.
One logical argument as well against the possibility of an eternal universe is the idea that eternity can contain an infinite number of singular time periods but no singular temporal period can contain eternity. As events within this universe can be ordered, this universe is contained within a singular temporal period. Because our universe is contained within a singular temporal period, it cannot be eternal.
Finally, can the universe create its own space and time or must something outside the universe create it? The only thing capable of creation is an intelligent agent. Why? The universe, based on experimentation and experience, operates on a set of natural laws and does not deviate from those laws. The universe is not an intelligent agent and is not capable of creation. Only an intelligent agent could create a universe that was orderly, held together by natural laws and structured within a set temporal period.
Because the universe had a beginning, it had a cause. The cause of the universe was an intelligent agent outside of the universe and outside of known space and time, namely God.
The Teleological Argument is an argument from design. The universe and everything in it has the appearance of design. Anything that has been designed, had a designer. Therefore, there was a God Who designed the universe.
Basically, if someone were walking along a beach and found a shell or a rock, they would assume that the rock or the shell had been created by some natural method. However, if someone walking along a beach had come across a watch or an airplane, they would not assume that it had been created naturally but that it had been created by an intelligent agent. Machines do not just appear through natural processes. Machines need a machine designer and creator. Likewise, the universe and the creatures contained within it give an overwhelming impression that they have been designed and not simply created from a natural process, without intervention from an intelligent agent.
Of course, some might point out that there are certain objects in the natural world that have the appearance of design. A boulder could be shaped just like the head of Abraham Lincoln. There could be a chicken nugget shaped like a cat. Just because something has the appearance of design does not mean that the object had been designed. In addition, there is a vast difference between an object that resembles another known object and an object that has intricate parts and precise arrangements, that possesses intelligence and has a unique function.
The universe, in fact, functions like a well-designed machine. There are numerous constants in the universe that, if they were changed in the slightest bit, the universe would not be able to sustain life. From the amount of carbon and oxygen to the power of gravity, everything is delicately balanced so that, if you modified any one of the constants by even a small percentage, life on earth would not be possible.
In addition, the design of the smallest component of life, a single-celled creature is often so complicated that it also gives sufficient evidence of a designer. And if something looks like a machine, then there must be a machine designer and creator. That Designer and Creator of the universe and everything in it was God.