 Let it be assumed that Plato is next to you and you know him to be running, but you mistakenly believe that he is Socrates, so that you firmly believe that Socrates is running. However, let it be so that Socrates is in fact running in Rome; however, you do not know this. (from Peter of Mantua’s De scire et dubitare, given in Boh 1985: 95)