The above quote by Tim Keller reminded me of a conversation that I had recently with one of my cousins who was raised Catholic and if anything is a nominal Catholic now as an adult. This conversation basically revolved around the above quote in whether or not Jesus rose from the dead and that is what everything revolves around and hangs on in Christianity.
Our conversation basically came to a point in which we had discussed the distinguishing differences between every other world religion and Christianity, discussed some of the different tribes or sects of Christianity, including Catholicism, and what it is that makes it true and different then the rest. Our twenty minute conversation revolved around the man Jesus Christ, his life, death, and resurrection. We already agreed that nobody can deny that there was a historical man named Jesus or that he was killed on a cross, but that what really makes the difference is the claim of a resurrection.
Being nominal Catholic there is a lot that she doesn't understand because she was never taught solid truth. So in the midst of our conversation she turned to me and said, "So basically if Jesus rose from the dead then the claims to Christianity would have to be true?" My response, exactly, it isn't whether or not you like his teachings, but that if he rose from the dead you have to accept all that he said as truth.
You see the only concept that she had ever been taught was a religious one in the sense that everything hung on her own behavior or that she would at least have confession with a priest when she had done wrong things so that they could be forgiven. She found exactly what she should have found, an endless cycle of meaningless confessions, by some man who cannot forgive or intermediate on your behalf for forgiveness. As with most Catholics I know this led to nominalism.
I wish I could tell you that she fully saw her need for the Savior Jesus Christ that day, but she didn't, not yet anyway. Everything was so seemingly new for her that she needs time to let it all set in from the religious baggage that she like many of us carry.
So to quote Tim Keller, I say to you as I said to my cousin, "If Jesus rose from the dead, then you have to accept all that he said; if he didn't rise from the dead, then why worry about any of what he said?"