How the Virtues Proceed From Unity
From this unity of heart is born inwardness or the internal life, for none can have inwardness unless he is one and united in himself; fervour or inwardness is the introversion of a man into his own heart, to comprehend and experience the internal operation or speech of God. Inwardness is a sensible flame of love, which the Spirit of God lights and kindles in a man, and a man knows not whence it comes, nor what has happened to him.