In their commentaries on the Sentences, Richard of Middleton, John Duns Scotus, William Ockham and Gabriel Biel reflect whether mentally-disturbed people can receive the sacraments (Baptism, Eucharist, confession, marriage) and fulfil juridical actions (make a will or take an oath). They consider that the main problem in 'madmen' in relation to the sacraments and legal actions is their lack of the use of reason. Scotus and Ockham especially are interested in the causes of mental disorders and the phenomena which happen in madmen's minds and bodies. In considering mental disorders mostly as naturally caused psycho-physical phenomena, Scotus and Ockham join the rationalistic mental disorder tradition, which was to become dominant in the early modern era and later.
Keywords: Baptism; Middle Ages; mental disorder; reason; sacrament.