How do we know that God is real?

Cosmological Argument

The cosmological argument states that every non-eternal thing that exists has a cause. The universe exists, so therefore something must have caused it. It is presumed that this cause is God. This argument is consistent with our experiences as humans. It is taken for granted that the universe exists. You can argue against the existence of the universe but you’d look rather silly. It is also taken for granted that everything has a cause. Once again, you can argue against that but you’d have a pretty difficult time doing so. In nature, we don’t observe spontaneous creation, we don’t observe events occurring without a cause, and we also don’t observe increases in order without external inputs of energy (Second Law of Thermodynamics). The creation of the universe defies all three of these and is therefore supposed to be the act of God because it defies other explanations.

Moral Argument

The moral argument states that objective morality exists. Therefore there must be a moral lawgiver behind objective morality. It is presumed that God is the moral lawgiver. It is taken for granted that objective morality exists. This can be observed in the masses. Across societies, humans tend to know what is right and wrong. Right and wrong can be a little gray but black and white exist. The majority of people on Earth would shudder at the thought of murdering a toddler for no reason. It is then taken for granted that these morals had to come from somewhere.

They could be attributed to evolutionary pressures but a lot of moral behaviors can’t be explained with that theory. For example, evolutionary biology is all about passing genes on to the next generation. A society that maximizes the amount of time the female population is reproducing while maximizing the production of food and required resources would have the greatest advantage compared to other societies yet these are not the morals we see developed in our societies. So, objective morality is instead attributed to being given by God, since he is the ideal being and therefore the source of moral values.

Teleological Argument

The teleological argument states that nature appears to be designed so therefore there must be an intelligent creator. It is presumed that God is the intelligent designer of nature. Of the arguments for God's existence, this one is probably the most feasible to prove. To disprove this argument, one must show that nature is not designed or that it was not designed by God.

The theory of evolution is usually used to attack the first premise but it falls a bit short on account of its lack of explanatory power in key areas. Areas that it can’t account for are the fine-tuning of the universe, the origin of specified complex information, and the problem of irreducible complexity. Multiverse theory or the long time frame excuse is usually given as a fallback but both fall short on the grounds of being just as unfalsifiable as God allegedly is.

Ontological Argument

The ontological argument is the least compelling argument for God’s existence in my opinion. However, it states that if the concept of the greatest possible being exists, then the greatest possible being exists in reality because by necessity a real greatest possible being would be greater than an imaginary greatest possible being. It’s kind of like saying the concept of the greatest man on Earth exists so therefore the greatest man on Earth must also exist. This is true but I’m skeptical of the logic scaling.

Religious Experience Argument

Last but not least, there is the religious experience argument for God’s existence. This argument is simple, God has revealed himself to humankind, therefore he exists. To disprove it, you would need to prove that God has not revealed himself to humankind. This one is the most pesky one for opponents of theism. If a given individual believes they’ve experienced an encounter with God, that’s not something you can talk them out of.

It would be similar to trying to convince someone their mother doesn’t exist right after a phone call with her. The usual approach is to point out inconsistencies from religious experience to religious experience. This is only partially effective because once someone’s seen the risen Lord on the road to Damascus, there isn’t any going back.

Conclusion: Don't Discount God

Of the arguments listed above, the cosmological, objective morality, and teleological arguments are pretty stout. They all present problems that the opposition doesn't have very good solutions for. So in conclusion, although you can't know God is for sure real with 100% certainty unless he reveals himself to you personally, you also can't know the Big Bang, evolution, or any other historical event that occurred was real with 100% certainty either. No matter what you do, at the end of the day, you're going to be taking a leap of faith. Given that's the case, it should be enough to at least get you to Pascal's wager.