Introduction to Logic

If an author writes “Q because P,” how can we tell whether he intends to explain or to persuade? We can ask: What is the status of Q in that context? Is Q a proposition whose truth needs to be established or confirmed? In that case, “because P” is probably offering a premise in its support; “Q because P” is in that instance an argument. Or is Q a proposition whose truth is known, or at least not in doubt in that context? In that case, “because P” is probably offering some account of why Q has come to be true; “Q because P” is in that instance an explanation.

Arguments that depend on rhetorical questions are always suspect. Because the question is neither true nor false, it may be serving as a device to suggest the truth of some proposition while avoiding responsibility for asserting it. That proposition is likely to be dubious, and it may in fact be false.

Questions can serve most effectively as premises when the answers assumed really do seem to be clear and inescapable. In such cases the readers (or hearers) are led to provide the apparently evident answers for themselves, thus augmenting the persuasiveness of the argument.