Why can't unbelievers understand what Paul teaches?

Les explains that Paul is always dealing in the realm of the believer, and the unbeliever cannot comprehend this. The reason is that these matters are beyond human comprehension; a person cannot believe them unless convinced this is the Word of God. Faith is not blind but documented—the substance of things hoped for and the evidence of things not seen. Through faith, by simply taking God at His Word, believers understand that the worlds were framed by the Word of God, that He spoke and creation came into being, and that things seen were not made out of things that appear.