Chapter — Vermeersch, On Chastity
Chapter III. On Restoring a Pure Life, or on the Amendment of Morals
Rationale of the order. The vices can be reduced to two kinds.
214. - Although the wounds to be healed are referred to three kinds - adultery, conjugal onanism, and solitary onanism - only a twofold lustful impulse is to be restrained in them and corrected by chastity, which we can call adulterous and onanistic. The former, as more physiological, betrays a corrupted love; the latter, as more psychological, manifests a disordered force of appetite; the former demonstrates a vice more in the object, the latter more in the subject. Nevertheless, a man is seen not so rarely to rush with a disordered force upon a forbidden object in such a way that he exhibits both vicious propensities.
But insofar as onanism is called conjugal, it indicates no new inclination of sense, but rather that fear of inconveniences or harms on account of which spouses offend nature, although the natural use of marriage affords a fuller delight of sense.