Seriously, is the distinction grammars drawn between τίς & τις overdrawn?
Semantically, do not both express indefinite meaning?
Is not the relationship between the two essentially the same as that between ἐμοῦ and μου? That is, distributionally, ἐμοῦ is used to express the discourse functions Topic and Focus, whereas μου is used to for completive or background material?
Is this not the exact same situation as the indefinite pronouns? Except that indefinite pronouns in turn also contribute to a differences in illocutionary force as well.