I […] define an argument as a sign which is represented in its signified interpretant not as a Sign of the interpretant (the conclusion) [for that would be to urge or submit it] but as if it were a Sign of the Interpretant or perhaps as if it were a Sign of the state of the universe to which it refers, in which the premisses are taken for granted.
http://www.commens.org/dictionary/entry/quote-letters-lady-welby-2