People continue to use a kind of "postmodern" understanding of what faith means to try and say that Christians ought to regard their beliefs as something fundamentally irrational. Here is part of a letter published in Nature:
Your Editorial about the promotion of ID in schools and universities (Nature 434, 1053; 2005) asks us to persuade our students that science and faith do not compete, but for Christians this should always have been clear. In the Bible (John 20: 25−29), Thomas doubts that the man speaking to him is the resurrected Christ until Jesus reveals his wounds. Thomas then believes, but Jesus says: "Blessed are those who have not seen and yet have believed".This section of John's gospel is often used in support of this claim, but by taking those two verses out of context, they are almost completely reversing the sense of what was originally written.
The Bible throughout teaches that faith is more valuable when expressed in the absence of evidence. For a Christian, when science is allowed to be neutral on the subject of God, science can only bolster faith.
Look at the next two verses:
Jesus did many other miraculous signs in the presence of his disciples, which are not recorded in this book. But these are written that you may believe that Jesus is the Christ, the Son of God, and that by believing you may have life in his name.Thomas saw and believed, and Jesus says that those who haven't seen and yet have still believed will be blessed. The question is: how are we who haven't seen supposed to know that Jesus is the Christ, the Son of God? This would be an understandable question long before the postmodern era. Is this supposed to be blind faith? An irrational leap in the dark?
No, says John. Jesus did loads of other things, but the whole point of me writing these things down is so that people who haven't seen can still believe. My eyewitness testimony is reliable, he says.
So faith isn't supposed to be blind - lacking in evidence. Faith is supposed to be based on knowledge that has been supplied by eyewitnesses.
Furthermore, elsewhere in the Bible, writers make it clear that regardless of whether or not a person accepts the validity of these eyewitness accounts, there is still enough evidence for them to know that there is a God - in the Old Testament, it says that "the heavens declare the glory of God". In the New Testament, Paul the apostle writes in Romans 1 that even though God is invisible, the nature of the universe tells us about what he is like. When the Bible talks about faith, it is certainly confidence in something that isn't seen - but that doesn't mean that the sense in the Bible is that it is a leap in the dark.
The idea of religious belief being something fundamentally irrational derives not from the nature of Christianity, but from the way in which existentialism and postmodernism have invaded all areas of public discourse over the last 200 years.