48. A certain learned man put a serious question to me, saying: ‘What is the gravest sin, apart from murder and denial of God?’ And when I said: ‘To fall into heresy,’ he asked: ‘Then why does the Catholic Church receive heretics who have sincerely anathematized their heresy, and consider them worthy to partake in the Mysteries; while on the other hand when a man who has committed fornication is received, even though he confesses and forsakes his sin, the Apostolic Constitutions order him to be excluded from the immaculate Mysteries for a number of years?’ I was struck with bewilderment, and what perplexed me then has remained unsolved 1.
1. 1Cf. P.G., 88; col. 912, Scholion 26: ‘Heresy is a deviation of the mind from the truth and a sin of the mouth or tongue, whereas fornication is a sin of the whole body, which damages and depraves all the feelings and powers of body and soul, darkens the image and likeness of God in man, and is therefore called a fall. Heresy comes from presumption, while fornication comes from bodily comfort. Therefore heretics are corrected by humiliation, and sensualists by suffering.’
We add the gist of a Greek note in K. A. Vretos’s edition of the Ladder (Constantinople, 1883, p. 91): ‘Obviously heresy is the greatest of sins. But since the passion of fornication has a tyrannical power due to pleasure and attracts attention, it often causes men to fall after repentance. Therefore, the fornicator is debarred for periods from the Holy Mysteries, that he may not return to his vomit and jeopardize his salvation. It also serves to put fear in all, and make them struggle against their passions and use the grace of the Holy Spirit. Heresy is a mental passion that springs from error and ignorance, or from ambition and vainglory. But when the evil is removed, it no longer causes conflict or trouble. Further, spiritual education aims at cutting out evil by the root. By the practice of a strict life, fornicators are trained to forget the pleasure of lust. For whereas the evil of heresy lies only in the mind, the passion of fornication also affects the body with corruption. The man who repents of heresy is at once cleansed by turning to God with his whole personality. But one who returns to God from fornication usually needs time and tears and fasting to get rid of the pleasure and heal the wound in his flesh and stabilize his mind. If, however, both remain unrepentant, they will certainly have the same condemnation.’
St. John Climacus, The Ladder of Divine Ascent, Step 15