 Most famously, Ryle (1949) introduced the idea of the category mistake as a way of dispelling the confusions he thought to be rampant in the Cartesian theory of the mind, and thus of dissolving many apparent problems in philosophy of mind. According to Ryle, one makes a category mistake when one mistakes the logical type or category of a certain expression (1949, 16–17). Thus, e.g., a foreigner would make a category mistake if he observed the various colleges, libraries, and administrative offices of Oxford, and then asked to be shown the university. The foreigner mistakes the university for another institution like those he has seen, when in fact it is something of another category altogether: “the way in which all that he has already seen is organized” (1949, 16). The category mistake behind the Cartesian theory of mind, on Ryle’s view, is based in representing mental concepts such as believing, knowing, aspiring, or detesting as acts or processes (and concluding they must be covert, unobservable acts or processes), when the concepts of believing, knowing, and the like are actually dispositional (1949, 33). Properly noting category distinctions may help alleviate a variety of philosophical problems and perplexities, and the idea of the category mistake was widely wielded (by Ryle and others) with this aim. Ofra Magidor suggests that it is “far from clear what Ryle took the central mistake in the dualistic position to be” (2013, 10). Jonah Goldwater (forthcoming), however, argues that, in The Concept of Mind, the category mistakes Ryle identifies all have the form of mistakenly conjoining entities that belong in two different categories – implicitly assigning their conjuncts to a shared category. But on Ryle’s view (Goldwater argues) there is often no single highest category (‘existent’) under which we can subsume the conjoined entities, and so we cannot sensibly conjoin, count, or quantify over them together. This, Goldwater argues, not only clarifies the basis for Ryle’s critique of both Cartesian and physicalist theories of mind, but also has the potential to dissolve various current debates in metaphysics, such as arguments against co-location that are based on denying (for example) that there is a statue and a lump both on the pedestal. Huw Price (2009, 330–335) argues that the category differences Ryle identifies can be seen as underlain by functional differences in the sorts of language used. The thought that category mistakes are symptoms of underlying functional differences, as Price puts it, suggests that to evaluate claims of category mistakes, and their relevance to traditional ‘metaphysical’ problems, we need “first-order scientific inquiries into the underlying functions of language in human life” (Price 2009, 335). Thomasson (2022, 23–29) picks up this idea, and begins to suggest how work in systemic functional linguistics can provide a way of understanding differences in linguistic function that may underlie a range of philosophical problems.