 How do we solve it? Anscombe thinks you can’t. In the bulk of the paper, Anscombe argues that the word ‘I’ isn’t a referring expression in a few steps. First, she argues that ‘I’ isn’t like other referring expressions: proper names, other pronouns, demonstratives, definite descriptions, and so on. So we can’t assimilate the use of the word “I” to other more tractable types of referring expressions. Second, she argues that the only remaining possibility is that the word “I” refers to an immaterial substance (a Cartesian ego), or at least a stretch of such a substance that exists so long as one is thinking a thought. But that would still leave us no way to identify the same referent in different “I”-thoughts at different times, an “intolerable” result. Moreover, Anscombe explicitly denied that there are immaterial substances. She described the very conception of an immaterial substance as “a delusive one” (IOS, 71).