Your question is a question that is perhaps the one that I am asked most often, and is probably the most important question that a thinking individual can ask. I think that anyone who is curious about the nature of all existence and the purpose of our lives will ask the question that you have asked.
I empathize with your question about proof for God's existence. I personally find the strongest proof that there is one God who created the world, took the Jewish People out of Egyptian slavery and gave us the Torah at Mt. Sinai to be the proof from Maimonides. God spoke to the entire Jewish nation and gave us the Torah "in person". Not via a prophet and not to an individual (Deut. 5:4). Our Torah teaches about the Creation of existence along with everything necessary for a purposeful and moral life in this world and the next.
The Sinai experience has been passed down from parents to children, from generation to generation, until today. It is the same history and teachings that are transmitted yearly at the Passover Seder, as well as daily in study halls throughout the world. This is the testimony of an entire people to the truth that they experienced thousands of years ago: there is one God who created the world, Mankind, gave us the Torah and is eternal.
Perhaps you would allow me to suggest that you try a Gateways retreat, class or other educational materials that we make available. The classes and the retreats offered by Gateways are excellent and cater to all ages and religious observance in an appealing and non-threatening way. You can see what I mean by checking out our site: http://www.gatewaysonline.org/
I also think that you might enjoy reading one of the classic books of Jewish philosophy called the Kuzari which is a book written almost a thousand years ago by Rabbi Yehudah haLevy in the form of a dialog between a Rabbi and a Gentile king. It is a theological debate between a Greek philosopher, a Christian, a Muslim and, finally a Jew. It is truly fascinating. There is an excellent translation (with footnotes) by Feldheim Press.
One particular article that we offer and I think you will find quite helpful is called “Historical Verification of the Torah” http://asktherabbi.org/DisplayQuestion.asp?ID=110 .
I wish you an enjoyable and fruitful “search” for the answer to your question. The fact that you even asked for more information shows that you are already well on your way to success. Please feel free to write again and ask about any questions you may have as you continue to learn.
