Saul Kripke On Unicorns

Kripke on Unicorns At the beginning of his first lecture in Naming and Necessity, Saul Kripke claims that he has a view about unicorns—namely, that he believes that there could not be, nor could there ever have been unicorns. Even if archeologists uncovered fossils deeps within the layers of the Earth’s crust, that had the shape of large horses with one horn protruding from their foreheads, this would not, Kripke believes, be evidence that there were or had been unicorns. Kripke explains his reasoning in his Addenda to Naming and Necessity. Kind terms such as ‘tiger’, Kripke thinks are rigid designators. This means that ‘tiger’ tracks tigers across counterfactuals, and across possible worlds. Therefore, like all rigid designators, they are
‘Unicorn’ picks out a mythical species, just as ‘tiger’ picks out an actual species. The only description we have of unicorns is just that—a description. And, as Kripke’s arguments against the descriptive theory of names supposedly shows, descriptions are not enough to track individuals across possible worlds. So while there may be creatures in other possible worlds fitting the description of a one-horned horse with magical powers, this description is insufficient for determining whether a certain animal is a particular species or not. In other words, many different species with many different internal structures could have satisfied the external appearances that we associate with unicorns. Kripke claims, “If we suppose, as I do, that the unicorns of the myth were supposed to be a particular species, but that the myth provides insufficient information about their internal structure to determine a unique species, then there is no actual or possible species of which we can say that it would have been the species of unicorns.” This is a metaphysical thesis: that no counterfactual situation could properly be described as one that involved unicorns. His second point is an epistemological