Andrew, I think you want me to enunciate why I am a Christian. I will begin to do so below, but I hope two things: (1) that it will open up a civil discourse, and (2) that at some point you will explain the primary reasons as to why you are an atheist.
The last few days, I have been thinking about how to answer this challenge, and have found it somewhat difficult. I finally understood why I am having trouble. To a Christian, our worldview is completely different. Trying to explain your viewpoint to someone who does not share your worldview can be difficult. C.S. Lewis summed it up well when he wrote, "I believe in Christianity as I believe that the sun has risen: not only because I see it, but because by it I see everything else."
Understand too that explaining why I am a Christian might actually take a book and it is difficult to summarize in a solitary blog post. As such, as long as it is amenable, I will offer several posts on why I am a Christian. This will only be the first reason for why I am a Christian.
The first reason that I am a Christian is because Christianity makes me a better person. If left to my own devices, I find that I become selfish, arrogant, and unloving. Being a Christian forces me to battle selfishness. Indeed, as Christians we are to treat others as more important that ourselves. This is a daily struggle, but it is a worthy struggle. When my life is not centered on Christ, I tend to be prideful and think that life is all about me. When I am not as serious about my faith as I should be, I become less loving and I note that I use people instead of treating them with love.
I am not alone in this. Other people I know who have become Christian see there lives radically change -- for the better. I know people who have overcome deep issues of bitterness and anger through their faith. I know others who have successfully battled serious addictions. For example, Alcoholic's Anonymous Twelve Step Program, is riddled with references to God and the need for His help.
Perhaps I am the only terrible person on earth, but I do not think so. I believe that man without the influence of religion, will be less loving, more selfish, more angry and full of bitterness. I am certain that what I am going to write next will be the source of much consternation, however, I think all religion, and Christianity in particular, helps people be better people.
I am certain the immediate objection from a non-Christian will be so-called Christians who commit vile acts in the name of religion. Already on this blog, you have said that often atheists are angry because they think that religion is harmful and causes people to do evil things. The example used was Harold Camping. It is not my place to condemn Harold Camping, but what I think what he did is despicable and there is little Christian about what he did. Yes, we Christians must take ownership for evil done in the name of God (the example I would use is the Catholic priests abusing children). I believe that evil committed by people who claim to be Christians is the largest hurdle that genuine Christians must overcome when convincing people that Christianity is truthful. To once again quote C.S. Lewis, "Of all badmen religious bad men are the worst."
I would address this issue in four ways. First, we Christians are fallible and make mistakes. Too often we Christians attempt to portray ourselves as "perfect." We are not and we should not pretend that we are. Rather, most of us struggle with issues and understand that we need help to live a better life. We fail on a regular basis and do not live up to our calling as Christians, but importantly we must be transparent about that. That is certainly the case with me.
Second, I believe that God will severely judge those who commit evil in the name of God. I believe that more than cursing using His name, this is what God had in mind with the commandment that prohibits "using the Lord's name in vain." Please understand I am not saying that people like Harold Camping who have done great evil in the name of religion are not Christians. That is not for me to judge. Whether or not people such as Camping are "saved", I do believe that God will judge them severely.
Third, it is not right to "throw the baby out with the bathwater." Christianity is true, whether or not there are people who use it for evil purposes. For example, there are people who blow up abortion clinics in the name of Christ. Because some idiot labels himself a Christian and attempts to wrongly justify his actions with Christianity does not mean that he accurately represents Christianity. Let's also be clear, there have been plenty of atheists who have committed untold evil. It is not right for me to say that atheism must be false because Lenin murdered millions of people.
Finally, people who do evil in the name of religion, although they are too prevalent, are an aberration rather than the norm. For every Catholic priest who abuses little children (even one is too many), there are thousands of good Catholic priests who defend children and help the brokenhearted. For every Harold Camping, there are thousands of us "normal" Christians who do good work at food banks, or volunteer at hospitals, or house the homeless. Although it is not where it should be (and shame on us), Christianity is responsible for more charity, philanthropy, and work to benefit the downtrodden than any other "system", atheism included.
This I know for sure, and it is the first reason that I am a Christian; namely, I am a better person than I would be if I were not a Christian. I am more loving, selfless, and less anxious than I would be if I were not a Christian. I know this because of times when I was "not walking close to God." In those times, my life was full of stress and anxiety; I was looking out for only one person; I was not always truthful with those around me; and I used people for my own ends instead of truly loving them. I do not think I am alone in this. I think that man left to himself will gravitate toward greed, anger, anxiety, bitterness, etc.