If you say that you believe in God and someone asks you why, "Because" doesn't cut it as an answer. And neither does, "Because I have faith..."  In fact, the word for faith in the New Testament comes from a Greek word meaning, "strong persuasion." 

When Paul was spreading the gospel, Acts 18 says, "he was reasoning in the synagogue every Sabbath and trying to persuade Jews and Greeks. " 

"Because" doesn't strongly persuade anyone. Our faith, our strong persuasion, needs to be reasonable. We need to be able to reason with other people in order to reach them. Are you ready, willing, and able?