Whenever a Christian converses with a non-Christian about the truth of the faith, every request of the non-Christian for the proof of Christianity should be met with an equally serious request for proof for the non-Christian’s philosophy of life. Otherwise we get the false impression that the Christian worldview is tentative and uncertain, while the more secular worldviews are secure and sure, standing above the need to give a philosophical and historical accounting of themselves. But that is not the case. Many people who demand that Christians produce proof of our claims do not make the same demand upon themselves….If the Christian must produce proof, so must others. (Desiring God [Sisters, Oregon: Multnomah Books, 1996], pp. 273-274)
H/T to Jason Engwer of Triablogue.