Now before I begin I want to let people understand something about faith. Everybody regardless of belief system (including atheism and agnosticism which I will get to in a minute) has a measure of faith to it. Faith being trust and belief in something that goes beyond their senses and into the realm of pure belief. I believe, though others may be free to argue, that everyone has beliefs that are basic and essential to them to function beyond their basic five senses:1. We all believe in the existence of person hood in others. That the people in our lives are people like ourselves.
2. We all could not function without memory beliefs. When I get out of work I get in my car and head home even though the existence of my home is not evident to my five senses.
3. People believe in love -- hold it, measure it, describe it visually, can you hear it, taste it. Hmmm. Seems love and other stuff like it are basic beliefs that are not really evident to the five senses.
Now -- atheists have this same problem though they deny it. They believe in a Big Bang -- they have never witnessed it. They believe in evolution -- ditto. Then they laugh at me for believing in a God, I can't see -- irony. There is an arrogance of mind to atheists who look in the face of their colossal ignorance of mankind about the universe and its nature and say they understand exactly how things were and are and will be. The statement --"There is no God" is ultimately just as big a statement of faith as "There is a God". Logically, 'There is no God' is a universal negative and universal negatives are the most hard to prove. To prove it you would have to be everywhere in the universe at the same time and have the power so nothing could block your ability to assess the question. This is not possible for any human and so the atheist is taking something very much on 'faith' when he says: 'The is no God.' It is actually a great leap of faith given that he is a finite being with a limited knowledge and only his limited education in his life and experiences to go on.
Agnosticism I can take better because they are at least willing to admit how ignorant they are and that there are some things that they may never know including whether there is a God or not. Most dismiss religion as an attempt to control and for the most part they are right. Most of the better ones though come back with the idea that there indeed may be a religion that is right, but how can you know which one? I understand the issues of agnosticism well because I considered it for a long year. I believe that it is a sensible option, but it may have its perils. Agnostics put faith in their reason and humanity much like atheists, but I think we can all admit that faith in both of these things can fail as well because of their limitations.
Now, what about the person who says -- There is a God. In some respect he is in a better position logically universal positives do not require as much effort to prove -- once you find evidence of God's existence that would be conclusive you can stop searching the universe. The problem is given the same limitations we can't do this either.
What we are left with is the hope that said God will reveal himself to us and show us He is real. Now that is what all religions in one sense or another claim has happened in one form or another. They all claim some divine revelation from a divine source that proves that their version of God, or the gods, or Karma or etc. is true.
What remains then is to assess if a religion has had a genuine visitation by the divine that can be verified. Which one the rises to a level where it stands highest in the most likely to be true.
Can we prove God exists conclusively -- no, but I believe that it is possible to prove which version of divine reality is the most true and provides the surest foundation for faith -- which all humans have.