Summa TheologiaePart II-II — Second Part of the Second Part Question 154 — Question 154 — The Parts of Lust Prooemium Article 1 — Whether six species are fittingly assigned to lust? Article 2 — Whether simple fornication is a mortal sin? Article 3 — Whether fornication is the most grievous of sins? Article 4 — Whether there can be mortal sin in touches and kisses? Article 5 — Whether nocturnal pollution is a mortal sin? Article 6 — Whether seduction should be reckoned a species of lust? Article 7 — Whether rape is a species of lust, distinct from seduction? Article 8 — Whether adultery is a determinate species of lust, distinct from the other species? Article 9 — Whether incest is a determinate species of lust? Article 10 — Whether sacrilege can be a species of lust? Article 11 — Whether the unnatural vice is a species of lust? Article 12 — Whether the unnatural vice is the greatest sin among the species of lust?