When you state a question or an argument, and your opponent gives you
no direct answer or reply, but evades it by a counter-question or an
indirect answer, or some assertion which has no bearing on the matter,
and, generally, tries to turn the subject, it is a sure sign that you
have touched a weak spot, sometimes without knowing it. You have, as
it were, reduced him to silence. You must, therefore, urge the point
all the more, and not let your opponent evade it, even when you do not
know where the weakness which you have hit upon really lies.