Should your opponent be in the right, but, luckily for your
contention, choose a faulty proof, you can easily manage to refute it,
and then claim that you have thus refuted his whole position. This
is a trick which ought to be one of the first; it is, at bottom, an
expedient by which an _argumentum ad hominem_ is put forward as an
_argumentum ad rem_. If no accurate proof occurs to him or to the
bystanders, you have won the day. For example, if a man advances the
ontological argument by way of proving God's existence, you can get
the best of him, for the ontological argument may easily be refuted.
This is the way in which bad advocates lose a good case, by trying to
justify it by an authority which does not fit it, when no fitting one
occurs to them.