In my latest reading of Same-Sex Unions in Premodern Europe, John Boswell argues against different interpretations of the ceremonies for same-sex unions in Christian Europe, particularly the ones that do not believe that the ceremonies concerned homosexual unions.
there's the view that the ceremonies concerned the spiritual love that
Christians are supposed to have towards one another. Boswell has a
problem with this proposal, for the ceremonies focused on two people
rather than groups of Christians, plus the ceremony was not permitted
for monks, which would be odd if the ceremony were about spiritual love,
since monks, too, were supposed to have that.
(UPDATE: Robert Wilken, who sees the rites as friendship agreements rather than same-sex unions, states the following about the ceremony and monks: "On occasion in Christian monastic literature one finds warnings
that monks should not participate in a ritual of 'making
of a brother' with someone outside of the monastery. Such
unions were prohibited monks because they entangled them in relations
involving money or property with persons outside of the monasteries." See here.)
Second, there's the
view that the ceremonies were about blood brotherhood, in which two
people form a bond by exchanging blood. But Boswell says that the
ceremonies do not mention blood, whereas blood is explicitly mentioned
during the Middle Ages when blood brotherhood is discussed.
there's the view that the ceremonies commemorated friendship. Boswell
considers this conceivable (and he notes earlier in the book that there
were friendships between males that were non-sexual). But Boswell notes
that the ceremonies do not mention friendship.
the view that the ceremonies concerned adoption. This view actually is
open to the ceremonies pertaining to homosexuality, for there were cases
in the ancient world in which adoption entailed "homosexual attachment"
(page 194). But Boswell notes that adoption is not mentioned, that the
ceremonies appear to create a relationship of two people joining
together rather than one being subordinate to another, and that there is
a reference to the couple, Serge and Bacchus. On page 147, Boswell
says that Serge and Bacchus were high-ranking Roman soldiers in the
third-fourth centuries who were close to one another, and they were
described similarly to how Tertullian portrayed a "Christian
heterosexual married couple" (Boswell's words).