A proposition (propositio) is an expression (oratio) signifying what is true or false; for instance, when someone says that the heaven is revolvable, this is called a statement (enuntiatio) and an assertion (proloquium). A question is a proposition brought into doubt and uncertainty, as when someone asks whether the heaven is revolvable. A conclusion is a proposition confirmed by arguments, as when someone shows by means of other facts (rebus) that the heaven is revolvable. A statement, whether it is said only for its own sake or brought forward to confirm something else, is a proposition; if one asks regarding it, it is a question; if it is confirmed [by other facts], it is a conclusion. So a proposition, question, and conclusion are one and the same, though they differ in the way mentioned above.
[Boethius, Boethius's De topicis differentiis, Stump, tr., Cornell University Press (Ithaca, NY: 2004) p. 30. Part of the point here, I take it, is to establish what it is that remains the same through dialectical inquiry -- we can have a question, which receives confirmation to be a conclusion, and then is affirmed as a proposition, and these three have to be in some sense the same thing, or you've just changed the subject, although they also have to be distinguishable.]
