A question asked without expecting an answer, because the answer is already implied, or because what matters is the doubt it exposes.
In Romeo and Juliet
What's in a name? That which we call a rose / By any other word would smell as sweet
Juliet asks "What’s in a name?" without expecting an answer, since the answer she wants is that there is nothing. The question already carries the thesis: the name is only a sound, with no power over what the thing is.