This being a Borges story, things are more complicated than the summary above. In particular, the older Borges concludes that, although they had met, the younger one had in fact been dreaming. What I am interested in here is whether the story puts forward a successful argument against solipsism.
Such an argument requires demonstrating the existence of another person, who is:
- essentially similar, enough to achieve meaningful communication, and
- sufficiently different, so that it cannot be a figment of the subject's imagination