Recently I started a discussion with an anonymous commenter on the post "Is 4-Point Calvinism Logical?" He is a skeptic about God's existance, but does not identify with an particular label which is fine. However, I felt I wasn't doing justice to my arguements due to the confined space of the comment page, so I am writing a series of post to engage with his (or her) arguements. I will refer to him in the masciline until corrected, and I'll be calling him Higgs, after the Higgs Boson particle (both because he brought it up and because I found it fitting for the discussion).
Higgs's main question is whether or not Christianity can be said to be logical, and is most curious about logical/mathematical proofs for the existance of God. I believe they do exist, and I will discuss four arguements for God's existance in this series. However, I want to make a different point first, and I will start with a thought experiment.
Let's say I endur some kind of accident which makes me forget my past. I have no idea who I am, and who my family is. However, due to the principals of logic and mathematics, and can prove that I do have parents. After all, I exist. This is sufficient evidence for me to conclude that there exists, or did exist, a man and a woman from who I came into being. This is true of all human beings, and since I am human it must also be true of me. This is mathematical; logical.
However, no amount of logic will tell me who my parents are: their names, occupations, passions, beliefs, class, or the extent of the rest of my family. I can sit in a room for hours, and think and think, and I will never figure that information out. It is impossible. In order to learn that, I must either research my/their history, or meet them. There is not other way.
The same is true for God. I believe that their does exist sufficient evidence and clear logic which demonstrate that God exists. But Christianity... that's another matter. Whether that God is Allah, Yahweh, Zeus, a lamp, or a flying speghetti monster, no arguement will ever prove God's identity. Nor will it be able to determine God's plan for existance, God's values, or God's relationship with humanity (though certain conclusions may be ruled out). In order to do that, you need revelation.
What is revelation? It is simply God being seen or heard; whether it be personal revelation (you meeting and interacting with Him) or recorded revelation (researching the history of God interacting with humanity). To demand Christianity to offer strictly logical proof for its particular view of God isn't really reasonable. The ultimate mistake that many atheists and the like make (and I am not including you with this statement Higgs) is the misunderstanding that Christians believe in God in order to explain natural phenonoma, like the beginning of the cosmos, etc... While we offer God as the agent for such things, we do not believe in Him in order to explain them. Neither do we accept God is a sufficient explanation, for the questions of who and how are incredibly different from each other. In fact it is our belief in the who that spurs us on to investigate the how. This was why the advent of modern science happened within the frame work of Christianity, not appart from it.
It is important that before we ask questions about God, we put such questions into the appropiate epistemological categories. Knowing the answer to who doesn't answer how, nor does answering how somehow demonstrate there isn't a who. Additionally, proving there is a God does not show who that God is, and that is not a question which reason and science can determine alone (though certain answers can be elimitated by reason). These are important things to understand as we approach the topic of proofs and arguments for God's existance.