... in relation to natural signs, there is no difficulty, since the visible connection there is between such signs and things indicates clearly that when we affirm of the sign the thing is signified, we mean not that the sign is really this thing, but that it is so in signification, and figuratively. And thus we may say, without introduction, and without ceremony, of a portrait of Ceasar, 'This is Ceasar', and of a map of Italy, 'This is Italy'.
antoine arnauld and pierre nicole, port-royal logic, 1662.
