There are many arguments for the existence of God that I believe are both valid and sound. However, some I think are more compelling (or should be) than others.
The following are what I believe to be the best logical arguments for the existence of God:
The Transcendental Argument:
1. Laws of logic exist and are binding on human thought.
2. If there is no God, 1 would not hold.
3. 1 does hold.
4. Therefore God exists.
(this is the abbreviated version. For a full version see: http://www.carm.org/transcendental-argument)
The Ontological Argument (Plantinga’s “victorious” model):
(Your understanding of this model will be greatly influenced depending on your understanding of modal logic.)
Maximal excellence: To have omnipotence, omniscience and moral perfection in some world.
Maximal greatness: To have maximal excellence in every possible world.
1. There is a possible world (W) in which there is a being (X) with maximal greatness.
2. But X is maximally great only if X has maximal excellence in every possible world.
3. Therefore X is maximally great only if X has omnipotence, omniscience and moral perfection in every possible world.
4. In W, the proposition "There is no omnipotent, omniscient, morally perfect being" would be impossible—that is, necessarily false.
5. But what is impossible does not vary from world to world.
6. Therefore, the proposition, "There is no omnipotent, omniscient, morally perfect being" is necessarily false in this actual world, too.
7. Therefore, there actually exists in this world, and must exist in every possible world, an omnipotent, omniscient, morally perfect being.
The Moral Argument:
1. Real moral obligation is a fact. We are really, truly, objectively obligated to do good and avoid evil.
2. Either the atheistic view of reality is correct or the "religious" one.
3. But the atheistic one is incompatible with there being moral obligation.
4. Therefore the "religious" view of reality is correct.
The Argument from Conscience:
This is actually not a formulated argument, but a follow up to the moral argument if someone objects to real or objective morality. We can then point out that they will all, no matter their convictions, universally accept that we should obey our conscience. Besides the fact that this actually functions as a universal, objective, obligation (“we OUGHT to obey our conscience”) we can still ask where did conscience get such an absolute authority—an authority admitted even by the moral subjectivist and relativist? There are only four possibilities.
1. From something less than me (nature)
2. From me (individual)
3. From others equal to me (society)
4. From something above me (God)
Let's consider each of these possibilities in order.
1. How can I be absolutely obligated by something less than me—for example, by animal instinct or practical need for material survival?
2. How can I obligate myself absolutely? Am I absolute? Do I have the right to demand absolute obedience from anyone, even myself? And if I am the one who locked myself in this prison of obligation, I can also let myself out, thus destroying the absoluteness of the obligation which we admitted as our premise.
3. How can society obligate me? What right do my equals have to impose their values on me? Does quantity make quality? Do a million human beings make a relative into an absolute? Is "society" God?
4. The only source of absolute moral obligation left is something superior to me. This binds my will, morally, with rightful demands for complete obedience.
Thus God, or something like God, is the only adequate source and ground for the absolute moral obligation we all feel to obey our conscience. Conscience is thus explainable only as the voice of God in the soul.
The Argument from Desire:
1. Every natural, innate desire in us corresponds to some real object that can satisfy that desire.
2. But there exists in us a desire which nothing in time, nothing on earth, no creature can satisfy.
3. Therefore there must exist something more than time, earth and creatures, which can satisfy this desire.
4. This something is what people call "God" and "life with God forever."