Introduction  Interpretation of the thema: the filius defunctus represents «the sinner in mortal sin»; the mater represents the «Church, which becomes a widow when the soul of a Christian dies due to mortal sin».
Divisio (see above) Twelve rules for recognizing mortal sin: 1) First rule: «mortal sin is that which is contrary to charity, which is the life of the soul» (reference to Thomas Aquinas, Summa Theologiae II-II, q. 59, art. 4), i.e. everything that is contrary to the charity of God and of the neighbor is a mortal sin; without charity, in fact, no virtuous action can benefit the salvation of human beings. 2) Second rule: «every transgression against the commandments of God is a mortal sin» (Increpuisti superbos: maledicti qui declinant a mandatis tuis [quote from Psalmi 118, 21]). 3) Third rule: «every transgression against the orders of the Holy Church is a mortal sin» (Si ecclesiam non audierit, sit tibi sicut ethnicus et publicanus [quote from Matthew 18, 17]). 4) Fourth rule: any transgression against the orders of one's ecclesiastical or secular superiors is a mortal sin, because qui potestati resistit, Dei ordinationi resistit (quote from Romans 13, 2); exemplum: not respecting the penance imposed by the confessor (reference to Duns Scotus, cf. General Notes). 5) Fifth rule: not only the act, but also the deliberate intention is a mortal sin; three phases of sin (reference to «a doctrine of St. Gregory» [from Decretum Gratiani, dist. VI, cap. 2]): 1. suggestion (not a sin); 2. unintentional pleasure (venial sin); 3. deliberate intention (mortal sin). 6) Sixth rule: «every pleasure of mortal sin is itself a mortal sin» (reference to Thomas Aquinas, Summa Theologiae II-II, q. 55). 7) Seventh rule: «he who, through his own fault, exposes himself to the risk of mortal sin sins mortally»; exemplum: if one knows that wine can inebriate him and, despite knowing it, gets drunk anyway, then he sins mortally. 8) Eighth rule: «he who consents to someone who commits a mortal sin sins mortally» (Digni sunt morte non solum qui faciunt ea, sed qui consentiunt facienti [quote from Romans 1, 32]). 9) Ninth rule: he sins mortally who, while not liking or approving the sin, gives occasion to others to sin («as established by civil law: “causing the occasion of damage is like doing the damage yourself”»). 10) Tenth rule: «He sins mortally who, while neither approving nor causing the sin, doesn’t oppose it as much as he can» (Error cui non resistitur, approbatur; the maxim is attributed to Gregory VII, but in reality it is by Innocent III [cf. Decretum Gratiani I, dist. LXXXIII, cap. 3). Any - temporal or spiritual - superior who is not aware of the sins of his subordinates and, therefore, doesn’t counteract them, commits a sin (reference to Liber extra, tit. XLI, cap. 10); similarly, one is responsible for the sins of one's godchild (reference to Decretum Gratiani III, dist. IV).
The eleventh and twelfth rules are voluntarily omitted («Lassiamo le altre due regule»).