Textual Criticism Texts - The Fluid Text: A Theory of Revision and Editing for Book and Screen by John Bryant (2002)

In this book, John Bryant argues that we shouldn't be talking about copy-texts; we should be talking about fluid texts.

What, according to Bryant, are the defining characteristics of a fluid text?

Why is it more useful to think about fluid texts—as opposed to copy-texts—when we're dealing with several, equally authoritative versions of a text?