When the Apostle Paul refers to walking by faith and not by sight, he is not suggesting that Christians deny reality. What's more, walking by sight is sufficient for some things, even certain issues of ultimate reality. Romans 1 tells us that the existence of God is confirmed by creation itself. While an intimate knowledge of God, the glorious Gospel of Christ and the promise of the age to come can only be known by special revelation and embraced by faith, there is natural evidence that the Scriptures which contain that revelation are reliable. Hebrews 11 contains a summary of various lives demonstrating what it means to truly walk by faith.