 As a result, while categories have continued to play a central role in analytic philosophy in the past century, and while some have continued to pursue work on categories in the realist spirit, others have shifted their focus to identifying differences in semantic categories rather than drawing out systems of ontological categories. Thus when Gilbert Ryle (1949, 1938 [1971]) talks of categories, he does not speak directly of categories of entities, but rather of differing logical types of concepts, where such type differences are detectable by the absurdities that result from substituting in terms of one sort for terms of another in sentences of certain kinds (see §2.2 below). Wilfrid Sellars, developing a strategy of Ockham’s, argues explicitly that we may construe category statements as disguised metalinguistic statements about the conceptual role of certain expressions (and their functional counterparts in other languages). According to Sellars, “Socrates is a substance”, for example, has the sense of “The ·Socrates· is a basic mental singular term”, and “Yellow is a quality” has the sense of “The ·yellow· is a (one-place) predicate (in mentalese)” (1970 [1974], 328) (where the “·___·” notation has the function of enabling us to speak about linguistic roles without being tied to a particular natural language). As a result, we can replicate the work done by traditional category distinctions between, e.g., substance and quality, without committing ourselves ontologically to the existence of qualities or other abstracta (1970 [1974], 329). On Sellars’ view, the categories are “metaconceptual, second-order functional classifications of the most fundamental types of first-order conceptual roles within a norm-governed linguistic practice or conceptual framework” (O’Shea forthcoming, section 1). An interesting upshot of this Sellarsian way of looking at the categories is that are not fixed, but may change over time as the conceptual roles in our norm-governed practices change (O’Shea forthcoming, section 2).