“Since we nowadays think that all a man needs for acquisition of truth is to exert his brain more or less vigorously, and since we consider an ascetic approach to knowledge hardly sensible, we have lost the awareness of the close bond that links the knowledge of truth to the condition of purity.  Thomas says that unchastity's first-born daughter is blindness of the spirit.  Only he who wants nothing for himself, who is not subjectively "interested," can know the truth.  On the other hand, an impure selfishly corrupted will to pleasure destroys both resoluteness of spirit and the ability of the psyche to listen in silent attention to the language of reality.”  --  Josef Pieper, The Silence of St. Thomas