 Following Rothschild (2007) and Nichols (in unpublished work; see  other internet resources),  we could say that while the name “Socrates” refers to an individual, the definite description “the teacher of Plato and Xenophon” can refer either to that same individual, or else to a particular role—namely, that of teacher to Plato and Xenophon. When understood in the second way, (3) means something like “The role of teacher to Plato and Xenophon might have been filled by a non-human”. Since we clearly can use definite descriptions to refer to roles, as in “The president is the highest office in the country”, the basic premise is not far-fetched.