"Sed Contra" is Latin and means "On the contrary," which is most notable, perhaps, from the Summa Theologica of St. Thomas Aquinas.
Thomas would begin each of his arguments with objections to his argument (Objection 1, Objection 2, etc...), then he would say, "On the contrary," followed (usually) by a quote from some authoritative source, then he would give his argument, followed by his reply to each objection (Reply Obj. 1, Reply Obj. 2, etc...); anyway, my using Sed Contra is just a Thomistic tip of the hat.