Christianity holds that it is by faith that people are reconciled to God. Faith, according to Christianity, is more than a virtue; it is necessary for salvation.

These days, the word “faith” is often used to mean something essentially irrational. Faith, in this sense, is belief in the absence of (or even in the face of) evidence. It is, by definition, unfounded.

This understanding of faith opens Christianity up to ridicule. Why would anyone embrace a religion than flies in the face of reason in this way?

It also undermines apologetics. If faith cannot be based in reason, then to go around reasoning with people in the hope of bringing them to faith is a waste of time, because if someone is persuaded to believe on the basis of evidence then they don’t have faith.

The above view of faith, however, isn’t the Christian view of faith. When Christianity speaks of the virtue of faith, it is not speaking of the virtue of irrational belief in God.

To see this, consider the paradigmatic case of a biblical figure who refused to have faith in the modern, irrational sense of the word: Doubting Thomas. When Thomas heard reports of Jesus’ resurrection, he insisted that he would not believe it until he had seen the evidence first-hand. Testimony wasn’t enough for Thomas; he wanted proof. He got it. Jesus showed himself to Thomas, and Thomas felt Jesus’ wounds, and he believed.

Thomas’s new-found confidence in the resurrection is repeatedly described using the language of faith. The word used in the New Testament for faith is “pistis”. This noun has a cognate verb, “pisteuo”, which, because “faithing” isn’t a word, is translated into English as “believe”. When we read about Thomas believing, we’re reading about him having faith.

Jesus says to Thomas, “Put your finger here and see my hands. Reach out your hand and put it in my side. Do not doubt but believe.” The word translated ”doubt” here is “apistos” (“without faith”); the word translated ”believe” is “pistos” (“faith”).

When Thomas has declared his belief, Jesus says, “Have you believed because you have seen me? Blessed are those who have not seen and yet have come to believe.” The word for believed here is “pepisteukas”; the word for believe is “pisteusantes”.

Thomas, as a result of seeing evidence of Jesus’ resurrection, came to have faith; Jesus said so himself. This shows very clearly that faith in the Christian sense need not be irrational. Whatever people are talking about when they say that faith is irrational by definition, it isn’t the same thing that Christianity commends.