This is the latest installment in an ongoing conversation I'm having with a friend who turned from Christian faith to agnosticism. Rationalism seems to be a common factor in many "de-conversion" accounts, and it has become a dominant topic in our exchanges. My friend has embraced science and rationality as primary epistemic sources, excluding the possibility of divine revelation. A previous letter discussed the use and limits of science. Here I am addressing the use and limits of rationality - and our desperate need for divine revelation.