Circumstantial faith is like a toddler with an egg...eventually its going to break and make a mess. Circumstantial faith is the idea that our belief system is based on events and experiences in our lives. Whether you adhere to a religion or a philosophy of life, this idea of basing what you believe, and consequently how you live your life, on what happens to you is dangerous. Why?
Three reasons: 1. We're not good at interpreting the events in our lives; 2. Our timeframe is too short; 3. We don't interpret the voice of God very well.
So often, a person may grow up believing in the Christian faith and its okay as long as things go their way. Then, eventually, the randomness and inconsistency of life kicks in and it challenges what they believe because they have adhered to circumstantial faith. Or maybe its the pleasures of life cause our beliefs to become inconvenient, so we adjust our beliefs to make the pleasures fit our convictions.
Its easy to do and to some extent we all do it. The important thing is to realize that the foundation of Christianity is not an experience. The foundation is the culmination of God's great rescue mission through the life, death, resurrection of Jesus Christ and the continual work of the Spirit on this earth and through His people.
So, what does your faith rely on? If its an experience or an event, its circumstantial and its fragile. If its foundation is God the father, Jesus the son and the Holy Spirit, its unchanging and consistent and strong.