Let me begin by making a few observations:
First, I know full well that atheists listening to this are not prone to changing their convictions and embracing the God of Scriptures.
Second, the Bible tells us that God is the one who draws men unto himself (John 6:44).
Third, what I present as a case for believing in God is my own testimony to the grace of God.
Finally, I have not heard all arguments against the existence of God, and even if I had (an impossibility) I would still not be persuaded to believe otherwise.
The genesis of this short introduction came after my reading of Van Til’s classic article Why I Believe in God. It is in that tradition of reasoning and apologetic that I find myself situated. I will also quote from him and follow his model of presentation, which began in childhood and concluded in his adulthood.
I had the distinct joy of being born into a Christian family. God was gracious to place me in such a home (Acts 17:26). It was there where my father, who happened to be a minister, trained me in righteousness. He was imperfect, as all fathers are, but the gospel was proclaimed daily in my life. “I was conditioned to believe in God,” as Van Til would say. God was a part of my day to day and part of my Lord’s Day. I worshiped as a child and continued to worship as a young boy. Yes, Christian religious training was poured down my throat, whether my parents understood what they were doing or not. The nurture they provided (Ephesians 6) was sufficient to establish a foundation for later years.
I was born in Brazil. I was born in a part of the country that was struck by poverty. Poverty was all around me. It is possible that an atheist may raise the question, “Where is your God now amidst all this poverty?” My answer is that He was right in the midst of it. You see, God does not reserve His presence only for the rich and prosperous. Where the poor sinner is, God is there also.
My early schooling was in the public educational system of northeastern Brazil. It was devoid of distinctly biblical education, though there was a lot more liberty to speak of religious things, in light of Brazil’s large Roman Catholic population. However, religious observations were scattered in a sea of mysticism and nominal Christianity. Yet, my joy was full. When I played soccer after school, I knew God existed. I never doubted for a moment. When school was over and I came home on Wednesday nights, I knew that it was time for prayer meeting. What did we do? We prayed fervently. We prayed without much order, but we prayed. It reminds me of Paul’s words in Romans 8: “26 Likewise the Spirit helps us in our weakness. For we do not know what to pray for as we ought, but the Spirit himself intercedes for us with groanings too deep for words.”
It was in those days when my father baptized me. Baptism is very important in Christian teaching. We often say that when you begin to walk away from the words of Christ, we should be dragged back by the hairs of our baptisms; and this happened over and over in my own life.
My education both at home and at school, though contradictory at times, was sufficient to mature my faith. Did I grow as a Christian as quickly as I would have liked? No, but I grew nevertheless. An atheist may find this statement non-sensical, but as Christians we like to talk about maturity in the faith; a little growth is still growth.
If you are an atheist who grew up in the Western World, I am sure that Christianity is not a foreign concept. If you are European, the names John Calvin and Martin Luther are ingrained in your history, though these days Europe is proud of its rejection of God. If you grew up in this country, you have heard of certain American forefathers, who though imperfect, believed in the God of the Bible. The reality is we were both born under the influence of Christian Civilization. So let me make this point clear, when I speak of faith in God, I am not referring to some abstract philosophical higher Being or the god of Islam or the god of Judaism. I am speaking of the Triune God of the Bible. As Van Til observes: “…surely there is no sense in talking about the existence of God, without knowing what kind of God it is who may or may not exist.”
I must confess that I was tempted in those early days. I was tempted to do that which the Bible considers to be sinful. What is a sin? A sin is any lack of conformity or transgression of the law of God. Yes, I confess I failed many times. But in biblical Christianity there is forgiveness. As Brit Hume has stated to the dismay of the media, “this is something Buddhism does not offer;” or any other anti-biblical religion or cult, I might add.
But yet, through continual repentance, Christ forgave my sins then, and continues to do so now. This is what atheists need to understand: Christians have never claimed to be perfect, without sin. What we have claimed is that when we sin, we have an advocate with the Father, Jesus Christ.
 As a reference, read Paedofaith by Rich Lusk http://www.athanasiuspress.org/inventory.html?catid=10
 Romans 8, English Standard Version
 Westminster Shorter Catechism, #6
 I John 1:9
 I John 2:1