“Saint Gregory Nazianzen calls the soul of the spiritual man - the mystic - an instrument played by the Holy Spirit:  organum pulsatum a Spiritu Sancto.  The Holy Ghost draws from this instrument harmonies and a melody of which reason and the will of man alone could never even dream.  It is this music vibrating on the well-tuned strings of a perfect human personality that makes a man a saint.  It is when special harmonies are wrung from a human instrument that the Holy Ghost makes a man a contemplative.  What part has reason in this silent song that God sings for Himself and for His elect in the soul of a mystic?  It is the function of reason not to play the instrument but only to tune the strings.  The Master Himself does not waste time tuning the instrument.  He shows His servant, reason, how to do it and leaves him to do the work.  If He then comes and finds the piano still out of tune, He does not bother to play anything on it.  He strikes a chord, and goes away.  The trouble generally is that the tuner has been banging on the keys himself all day, without bothering to do the work assigned to him:  which is to keep the thing in tune.”

[The Ascent to Truth:  Chapter XII, pgs. 181-182]