Reason without sacred writings is like a tool with nothing to use it on, but sacred writings without reason can be a blind leap in the dark in the search for spiritual truth. Both should work together to discern truth from falsity.
All in truth
How Can We Know if We Know Anything?
Research has shown that certain fundamental laws of logic and mathematics are 'pre-programmed’ into an infant’s mind. This enables them to recognize there is an external reality and allows them to start reasoning and accumulating knowledge. But how can we be confident that what we think we know is true?