John Cassian, Conferences I–X IX.27: Of the different sorts of conviction

But how and in what way those very convictions are produced from the inmost recesses of the soul it is no less difficult to trace out. For often through some inexpressible delight and keenness of spirit the fruit of a most salutary conviction arises so that it actually breaks forth into shouts owing to the greatness of its incontrollable joy; and the delight of the heart and greatness of exultation makes itself heard even in the cell of a neighbour. But sometimes the mind hides itself in complete silence within the secrets of a profound quiet, so that the amazement of a sudden illumination chokes all sounds of words and the overawed spirit either keeps all its feelings to itself or loses them and pours forth its desires to God with groanings that cannot be uttered. But sometimes it is filled with such overwhelming conviction and grief that it cannot express it except by floods of tears.