Instance. Ever since Bacon and perhaps his contemporaries(1) this word has
borne the sense of example. Any case of a rule or principle is called an
instance of it.
For instance is a form of speech altogether equivalent
to for example. By the schoolmen, however, instantia was used for the Greek
ἐνστάσις, of which it is the exact translation. This means an
the bringing forward a case to the contrary of what has been laid down.
So that the phrase an instance to the contrary would have been in
their lips redundant.(2)
(1) Vide SHAKESPEAR'S Wise Saws and Modern
(2) DE MORGAN, Formal Logic, p. 236.