This first section would be more accurately described as Theology 101, as it presents the arguments and appropriate counterarguments for the potential existence of a god. These are the arguments that the religious should be using, being that they are the only time reason and logic coincide with belief in a god. But sadly, most tend to stick to the circular logical fallacies along the lines of 'The Bible is the word of God because the Bible says it is.'
There are 3 decent proposals for the existence of a god, each with its own glaring faults:
1. Cosmological Argument (aka First Cause Argument, aka Universal Causation)
The First Cause argument is based on the nature of causality, or 'cause and effect' structure of life. Everything that exists has a cause. Bypassing the bulk of the causality/contingency nonsense, basically the argument is that nothing can will itself into existence. Your parents created you and their parents created them and so on and so forth. But since people can't grasp the concept of infinity, they suppose that there had to be a 'First Cause.' A self-sustaining, causer of all things; a first domino to start the chain of causation that leads to present day existence, which we call 'God.'
The first and most obvious argument against this is, 'If God is the cause of all things, then who caused God?' (insert 'created' instead of 'caused' for Intelligent Design buffs). The cosmological argument is contradicting by its very design. If there has to be an exception to the continual chain of dominos, a 'first' domino, exempt from the rule, doesn't that imply that the rule itself is flawed? Everything that exists has a cause of its existence.
If God exists but
does not have a cause of his existence then the premise is false, in
which case the simple cosmological argument is unsound. If the premise
is false, i.e. if some things that exist do not have a cause, then the
cosmological argument can be resisted on the ground that the universe
itself might be such a thing. If God is claimed to exist uncaused,
then the cosmological argument fails. Or instead of filling the first domino role with a father figure God, why can't the First Cause be the Big Bang? It would make more sense than assigning a human-esque, big brother who watches all from his realm in metaphysics land. The universe, and all its matter, are constantly expanding. So one would think that following time backwards to the origins, the universe would have to have been compact or in a form of implosion before expanding outward, providing more support for science than for mythical beings.
2. Teleological Argument (aka Design Argument, aka Watchmaker Analogy)
The argument is that when observed, the world is complex, with various systems of order that maintain life. Anything that intricate and complex could not have come about by chance. Similarly, when examining a watch, you can see that it has complex parts all acting in harmony towards a purpose. Just as the complexity, order, and purpose of a watch implies
intelligent design, so too the complexity, order, and
purpose of the universe implies intelligent design.
Like the First Cause argument, the first question that arises is one of infinite regress. "We are the designer of the watch, God is the designer of us…so who designed God?" More self defeating circular logic. And also, complexity does not necessarily imply a designer. It's been suggested that diamonds and snowflakes are intricate and complex in nature, yet they are formed in the controlled chaos of nature.
Also like the First Cause argument, none of this is any proof for existence of God. A scenario is set up in a way that God can be forced in as explanation, but the x factor can just as easily be a multitude of sentient beings, or Shiva, or the gods of Greek mythology, or a magical pink unicorn that jumps between universes and creates life.
3. Ontological Argument (aka the Complete Nonsense Argument)
I'm not sure how the Ontological Argument came to be regarded as a coherent, legitimate argument, as it makes no sense to me and the majority of the philosophical world. Basically it goes like this:
I exist.
I can conceive of a perfect, supreme being.
Being a perfect being, it must exist or else wouldn't be "perfect."
Therefore God exists.
This is more or less the argument, as I'm tired and don't feel like going into the semantics of the setup. Regardless, its because I, a being that exists, can conceive of a perfect being, this perfect being must exist or forfeit its perfection. This is immediately discarded in my psyche because I can also conceive of a perfect purple dragon, which none greater can be conceived, floating outside my window and yet this neither justifies what is and what isn't. What can be conceived in the metaphysical realm of the mind isn't correlated to what does or doesn't exist in the material world.