The fire that Moses saw was not by any definition what we know as fire, for it did not burn the blazing bush. The light that shone from Christ in his Transfiguration was not what is light in the canons of natural physics, because it was of an intensity beyond accessible description without damaging the eyesight of Peter, James and John.

Fifty days after the Resurrection, in the upper room, there was a noise “like” a driving wind and then flames “as of” fire shone over the heads of the apostles, but the description required similitudes because the noise and the flames were not a natural noise and fire.

“Grace does not destroy nature, but perfects it.”

Christ promised that the Holy Spirit would enable human intelligence to embrace depths of reality beyond the limits of natural experience. Here at work is the principle of Saint Thomas Aquinas: “Grace does not destroy nature, but perfects it.” The apostles became more intensely human when they received the power of the Holy Spirit, to the extent that they traveled to lands beyond the limited environs of their early years, with a courage never before tested.

They received the “glory” that Christ, on the night before He died, prayed that His disciples might share. Because that participation in the divine nature bridges time and eternity, there is an invigorating terror about it: not the dread of being diminished or annihilated, but the trembling awesomeness of breaking the bonds of death itself.

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When the Holy Spirit moves a man from aimless biological existence to what Christ calls the “fullness” of life, the reaction is a little like that of someone who has heard simple tunes but then encounters a symphony. Simple pleasure may evoke smiles and then laughter, but the deepest joy can move one to tears, and that is why there is that curious experience not of laughing for joy but of weeping for joy, and the equally enigmatic experience of lovesickness.

Often quoted is the diary account by Samuel Pepys in the 17th century after attending a concert: “… that which did please me beyond anything in the whole world was the wind-musique when the Angel comes down, which is so sweet that it ravished me; and endeed, in a word, did wrap up my soul so that it made me really sick, just as I have formerly been when in love with my wife.”

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A fan of Jascha Heifetz told him after a performance that his violin had such a beautiful tone. The maestro placed his ear against the Stradivarius and said, “I hear nothing.” By way of metaphor, it may be said that we exist biologically as wonderful instruments: The brain itself is the most complex organism in the universe. But we make celestial music only when the Holy Spirit conjoins our human nature with the source of life.

Fr. George William Rutler is a Catholic priest and the pastor of the Church of St. Michael in Manhattan. This article, which originally appeared in his parish church bulletin, is used by permission.