Hostiensis (d. 1271) and the girl called Peter
Henry of Segusio (d. 1271), cardinal-bishop of Ostia and hence better known as Hostiensis, was an eminent jurist of the thirteenth century. His Summa of the Decretals, written in the 1250s, was widely praised as Summa aurea (‚The Golden Sum‘) and belongs to the most important works of medieval jurisprudence. Among many other legal question, he also dealt with the legal gender of hermaphodites; specifically, he argued that true hermaphrodites (which could not be assigned male or female gender otherwise) could, and indeed had to choose their legal gender under oath (Summa aurea ad X 2, 20). Well into the nineteenth century, this doctrine was not only taught at the universities, but applied in ecclesiastical courts well into modern times (see Santi 1886-98, vol. 4, 277 for a case decided in the late 19th century, and Rolker 2014 more generally).
Hostiensis also dealt with sex and gender in a completely different context. Commenting on the sacrament of baptism (Summa aurea ad X 3, 42), he brings up the question what happens if a girl is mistakenly thought to be a boy, baptized, and given the name Peter:
But what if someone thinks he is baptizing a boy, whom he gives the name Peter, but the child happens to be a girl – does this baptism not lack [sacramental] efficacy? This indeed seems to be the case, because there is an error concerning the sex […]. However, it does not seem to be the case that such errors impede baptism. As far as the worship of God is concerned, there is no male and female, neither slave nor free [see Gal. 3:28], and even if one errs concerning the sex, he does not err concerning the person whom he holds and whom he intends to baptize.
Quid ergo si quis putet baptizare puerum, cui imponet nomen Petrus, cum forte sit puella – nunquid baptismus caret effectu? Videtur quod sic: quia in sexu erratum est […]. Sed contra, quia non videtur, quod tales errores impediant baptismum. quantum enim ad Dei cultum non est masculum, neque femina, neque liber, neque servus [see. Gal. 3:28], et licet homo erret in sexu, non errat in personam, quam tenet, et quam baptizare intendit.
Source: Henrici de Segusio, Cardinalis Hostiensis, Summa aurea, Venice 1574, here at col. 1192 [Google books]; own translation.
In other words, the bodily sex of the candidate for baptism (including errors concerning her or his bodily sex, or gendered names not matching his or her sex) cannot possibly affect the validity of the sacrament.
Henrici de Segusio, Cardinalis Hostiensis, Summa aurea, Venice 1574. [Google books.]
Christof Rolker, ‚The two laws and the three sexes: ambiguous bodies in canon law and Roman law (12th to 16th centuries)‘, in Zeitschrift der Savigny-Stiftung für Rechtsgeschichte, kanonistische Abteilung 100 (2014), 178–222. [DOI: 10.7767/zrgka-2014-0108]
Francesco Santi, Praelectiones juris canonici, quas juxta ordinem decretalium Gregorii IX. tradebat in scholis pont. seminarii romani, 5 vols., Regensburg 1886-98.