/summa/XP/XPII/XP_Q58:
We must now consider five impediments to marriage, namely the impediments of impotence, spell, frenzy or madness, incest, and defective age. Under this head there are five points of inquiry:
(1) Whether impotence is an impediment to marriage?
(2) Whether a spell is?
(3) Whether frenzy or madness is?
(4) Whether incest is?
(5) Whether defective age is?