The structure of a medieval quaestio, e.g. each article in
the Summa Theologiae
(1) The posing of the question
(2) Objections to the position that the master (magister) will
ultimately defend
(3) The sed contra: most often a brief Scripture quote or
passage from a Father of the Church or a philosopher suggesting the
position that the master will defend
(4) The responsio, or body (corpus) of the
article: the master's determination of the question
(5) The master's reply to each of the objections posed at the beginning.
Imagine a lecture hall (aula) filled with students--some
sober, some not--on a feast day. The question is posed, and students
begin to yell out objections from the audience (no microphones
necessary). A scribe is writing down the objections, perhaps to be
edited later in the case of less-than-sober objections. The master (or
one of his faithful student-lackeys) comes up with a sed contra.
At that point the master makes his determination and then replies to
the objections.
The Summa Theologiae is not itself the record of such a scene
(though several of St. Thomas's works--the so-called "Disputed
Questions" (quaestiones disputatae) are indeed doctored records
of such scenes), but St. Thomas nonetheless wrote the Summa
Theologiae in the same style.
Note: Given this structure you
should be careful not to attribute to St. Thomas any quotations taken
from (1), (2) or (3). He speaks in his own voice only in (4) and
(5).