The reason sees the small and the larger but not the large. It sees the preliminary, but not the final, the derived but not the original, the complex but not the simple. It sees what is human but not what is divine.
Source, in full
"The Righteousness of God" (1916) in The Word of God and the Word of Man (1928) as translated by Douglas Horton; this passage begins with a quote of Isaiah 40:3-5; often quoted alone has been the phrase following it: "Conscience is the perfect interpreter of life."