A rhetorical question, in simple terms, describes a question often based on rhetoric that
does not necessarily require an answer. In fact, it is often a way of making a tentative statement but phrasing it in the form of a question. Frequently, a rhetorical question is a tool people use in debate to avoid making an outright declaration, but at the same time still being able to make a point. If called out on the point later, or shown that it was not accurate, the speaker can then claim it was only a question.
http://www.wisegeek.com/what-is-a-rhetorical-question.htm
