I believe that God exists because of the evidence. Three of the most convincing arguments that really solidified my faith in God are the Kalam cosmological argument, the moral argument, and the fine-tuning argument. Theism simply explains the creation of the universe out of nothing, objective moral values, and the constants that make human life possible. Atheism utterly fails at explaining those things.
The Kalam cosmological argument goes as follows:
1.) Everything that begins to exist has a cause.
2.) The universe began to exist.
3.) Therefore, the universe has a cause.
The first premise is pretty obvious. Things do not just pop into existence uncaused out of nothing. For every effect, there is a cause. This is constantly verified in our experience and never falsified.
The second premise is supported by several lines of evidence. There are two philosophical arguments for the impossibility of an infinite past (which I will not go into in this post for the sake of space). There are also two empirical evidences that the universe began to exist.
Most scientists agree that the universe began to exist a finite time ago, since the universe is expanding and, if you go back in time, will contract back into a singularity in which all matter, space, and time come into existence.
Also, the laws of thermodynamics tell us that in a closed, isolated system (such as our universe), the amount of usable energy is running down. Since the usable energy in our universe has not completely run down into a state of equilibrium, the universe must have begun a finite time ago.
So, since everything that begins to exist has a cause, and the universe began to exist, then the universe must have a cause. Not only that, but since the cause is the cause of all matter, space, and time coming into existence, the cause must be immaterial, nonspatial, and timeless. Furthermore, there are only two types of entities that could be timeless, nonspatial, and immaterial: either abstract objects (such as numbers) or a personal mind. Since abstract objects are causally impotent, the cause must be a personal mind. So, there must have been a transcendent, immaterial, nonspatial, timeless, personal being who brought the universe into existence out of nothing. That cause is most plausibly God.
The moral argument can be formulated as follows:
1.) If God does not exist, objective moral values and duties do not exist.
2.) Objective moral values and duties do exist.
3.) Therefore, God exists.
Most atheists will agree to premise (1). If there is no God, there is simply no way for there to be an objective standard of morality. Morality is simply left up to personal opinion and culture.
The second premise is the main point, and seems intuitively obvious to most people. Most people would agree that torturing babies is objectively wrong no matter what culture you live in. Most people would agree that burning a widow alive after the death of her husband is objectively wrong regardless of personal opinion. Most people believe that the holocaust was wrong, and would still be wrong even if the Nazis had won WWII and killed or brainwashed everyone who disagreed with them so that it was universally believed that is was right.
So, if you agree that those things are objectively wrong, then you are logically committed to believe that God exists. He is the only way moral values and duties could be objectively grounded. Moral values are grounded in His unchanging nature, and moral duties are derived from His commands, which are necessary expressions of His good and loving nature.
The fine-tuning argument can be formulated as follows:
1.) The fine-tuning of the universe is the result of either physical necessity, chance, or design.
2.) It is not due to physical necessity or chance.
3.) Therefore, it is due to design.
There are multiple physical constants that are incredibly fine-tuned (e.g., the electromagnetic interaction, the weak force, strong force, gravitation, the ratio of proton to electron mass, etc.) so that if they were slightly altered just one way or another, life could not exist.
This fine-tuning could not just be by chance. For every one of these constants to just happen to be at the precise quantity at the same time so that life could exist is just ridiculously improbable.
The fine-tuning could not be by physical necessity. It is certainly possible that the different constants could be otherwise. If someone believes the constants are the result of physical necessity, then they have to present a tremendous amount of evidence for that.
So, it must be by design. A design requires a designer. So, I believe that fine-tuning is good evidence that God exists.
All these arguments together provide a compelling case for the existence of God.
