This material comes very near the end of a very long paper in which Sellars criticizes what he calls the "Myth of the Given." This "myth" is the conviction, which can be traced back to Descartes, that our empirical knowledge is founded on sensory appearances that are not open to doubt (cf. Descartes's claim that while I may not really see a light, I "certainly seem to see" and that "this cannot be false," p. 12, col. 1, in Chalmers). Sellars completes his critique of this view with an alternative account of sensations that presents them as theoretical entities; in the analogous account of thought that you will read, he is laying the groundwork for his account of sensation.

• Sect. XI. This sets up the problems that Sellars will try to solve. The key passage is his revision of the "classical" view of thoughts as stated on at the end of the first paragraph of §47 (p. 534).
• Sect. XII. Sellars leads up to his account of thoughts and sense impressions by seeing what must be added to a language to introduce talk of such things. The language of "our Rylean ancestors" is the starting point. He describes it in §48, considers a first addition to it in §49, and in §50 points to the further additions necessary to complete the project he set for himself in sect. XI. Sellars calls the language of these ancestors Rylean because it provides the resources that Ryle used for his logical behaviorist account of mental states and processes.
• Sect. XIII. Sellars here begins stating his account of things mental by considering the nature of theoretical language. You can compare what Sellars says about a special use of "in" and "is" with Place's "'is' of composition." Notice that this sort of language constitutes a further development of the Rylean language game (see the end of §52).
• Sect. XIV. By the end of this section, Sellars has used the ideas about the language of theory from sect. XIII to lay the groundwork for his account of thoughts and impressions. The sort of account he offers of our use of vocabulary for the mental has has sometimes been referred to as the "'theory' theory." Think about what might lie behind this label. Although Sellars describes his view as "behavioristic," it is probably closer to functionalism. You've seen the term "behaviorism" used more often for the sort of position Sellars describes as "unduly restrictive" at the end of §54, p. 538, col. 2.)
• Sect. XV. Here Sellars recounts the invention of the language of thoughts by the culture hero Jones, who he introduced in §53. Notice especially the account in §59 of the first person use of this language in a reporting role.

After the selection in Chalmers ends, Sellars goes on to give an account of sensation. It is analogous to what he says about thought except that, in the case of visual sensation, the model for sensations are not speech episodes but rather replicas of things seen. That is, visual sensations are states that have relations to each other and to things seen that are analogous to the relations holding of replicas of things seen.