Faith does not exist on its own. It must be connected in some way to truth. Otherwise, we believe a lie. At the same time, however, the truth we believe in as Christians is not the same as factual or scientific truth. In other words, we believe in some things we cannot prove.
We might call this “revelational” truth, begun first in scripture, but then confirmed by tradition. This is truth that has been verified, not be the nature of itself (which is beyond the means of measurement per se), but by the application of it to life. It is what some today are calling “lived theology.” It is belief validated by practice.
The claims of Christianity are true because, when accepted and embraced, they produce what they claim. The lives of the saints are the “living testaments” to faith.
The authenticity of revelational truth is as genuine as factual truth, but whereas natural law undergirds factual truth, people undergird revelational truth. Collectively, this is the witness of the Church, manifested by its teaching and example. We trust in this kind of truth as much as we do the convictions of science.