A counterargument is a reason offered against a position, raised inside an argument that ultimately resists it: the writer states the opposing case in its own strength, then answers it. The move belongs to rhetoric and composition teaching, where it has been described under many names and with varying accounts of how it relates to concession, refutation and objection. What the term denotes is a convention of good faith in argument, not a rule anyone enforces. Style guides recommend it, teachers require it, logicians analyse its structure — and the boundary between anticipating an objection and merely acknowledging one is drawn differently by different writers. The practice and the reason for it are what this entry can honestly give.
Why this entry carries no source list. This lexicon cites an official primary source wherever one exists, and says so plainly where none does. No body governs this term. There is no standards organisation for it, no register, and no text whose authors could claim to have settled its meaning. Methods literature describes practice and argues about it; a citation to one author would dress a position in a live argument as a rule, which would mislead more than silence does. What follows is the convention as it is actually used, with the disagreements named rather than smoothed over.