Plea for a theory of open texture

I will consider a class of cases sometimes said to exemplify the open texture of language. They resemble some cases familiar from the mid-20th century. Consider J. L. Austin’s famous example of a bird that, for all the world, looks like a goldfinch, and then blows up like a grenade. Is it a goldfinch? A more realistic case involves the word “book” as used around 2000: were utterances such as eBooks are books true around this time? Hard to say. We can imagine a separation, where British speakers affirmed such sentences, and Americans denied them, without either appearing to misapply “book.” Is this kind of open texture a more well-studied linguistic phenomenon? I argue, first, that such cases resist both metaphysical and epistemic explanations. Then I argue that openness cannot be identified with partial definition, vagueness, non-vagueness indeterminacy, or underdetermination. This provides reason to think that, if there is any such thing as open texture, it is sui generis and worthy of its own theory.