Paul is pointing out to us in a powerful way that our entire faith and our entire life is built upon one historical event, the resurrection of Jesus Christ. If He rose, we have eternal life. If He did not rise, then we are "of all men the most pitiable." We are living a life of lies and deceit.
The most important question for humanity: did Jesus Christ rise from the dead?
The most important question for each human: do you believe that Jesus Christ rose from the dead?
All other questions hinge on the answers to these two.