The last posting on this topic considered the third movement of the first chapter of Sellars' book Science and Metaphysics and concluded with a comparison of Sellars' view of Kantian intuition and that of Salomon Maimon. In this posting I am going to consider the fourth movement of the first chapter.
The fourth movement opens with a series of questions concerning the status of "sense impressions" considered as the content of "sheer receptivity". The basic question considers whether the "sense impressions" need to be considered as states of consciousness (albeit non-conceptual ones) that intervene between the causal impact of the external environment on the mind and the verbal expression indicating a referential relation to the environment. Rather than see the "sense impressions" this way it could be the case, as is suggested by contemporary physicalists, that all we need to discuss is physical states. In which case, the relationship of guidedness between the referential verbal report and the environment on which it reports would simply be carried out by the physical operations alone. Here, it is interesting to see how Sellars, whilst maintaining a framework of scientific realism, moves away from the standard responses of physicalists.
What the appeal to the notion of the "sense impression" involves is a kind of state that is neither conceptual nor physical and, in making this appeal, Sellars resists classical intellectualism on the one hand and brute physicalism on the other. (Here we see his intellectual kinship to Kant and why the Kantian reference is important to him.) The rationale for the "sense impressions" remains one of accounting for the appearance of conceptual representation within the general awareness of perceptions. Particularly, it is meant to help deal with what we might think of as "minimal conceptual representations" even though, as indicated in the third movement of the chapter, Sellars does not take it to be the case that all visual perception need involve these.
The basic question concerns one of a correlation between the physical objects on the one hand and the mental states that have a connection to them. This is expressed again, as was the case in the third movement, through an analytical response to the way that conceptual representations occur. So, the example is given that, under "normal" circumstances there are perceptions of a red and rectangular object in specific circumstances. The circumstances are when we are in some causal relationship to the object. Another situation in which the perception of this type occurs is an "abnormal" one where something else than the specific object is affecting us due to its possessing, in some sense, characteristics that are related to the object.
What Sellars wants to account for is not a set of behavioural characteristics such as are displayed when someone consistently shows they can distinguish between "red" and "blue" accurately. It is rather the ability to conceptualize the experience that is at issue. The basic problem is thus not one that concerns the second case mentioned in the last paragraph (the "abnormal" one) but the first case (the "normal" one). How is that the conceptual occurrence of the description of the datum is given when confronted with something that referentially matches said datum? In responding to this Sellars wishes to invoke the "sense impression" as what is at work in "guiding" the conscious state such that the "sense impression" immediately corresponds to the causal stimuli that brings it about. (This "immediate" element of the "sense impression" is also a connection of it to the Kantian sense of intuition.)
There has to be something about the "sense impression" that makes it, in a way that does not apply to the verbal conscious report, analogous to the causal stimuli that brings it about. Rather than invoke this notion Sellars mentions that we could have one of two alternatives that might seem to dispense with the need for it. We could, on the one hand, claim that the capacity in question, is innate. On the other hand, we could just deal with it, in quasi-Wittgensteinian terms, by speaking about induction into a language-game. Sellars does not attempt, however, to deal here with the rationalist appeal to innatism but simply leaves that suggestion aside.
Sellars' response to the quasi-Wittgensteinian view is more interesting. The point he makes here is that, in order for this induction into the language-game to work, there must already exist the possibility of some cues for connection between verbal reports and causal and physical stimuli which the story in question presupposes and cannot explain. The account is, in fact, part of a story of generational connection but not really one that makes clear how such connection can take place at all.
Going back to the question at issue Sellars distinguishes between the sense that there are impressions of red rectangles simpliciter and impressions that red rectangles are located in specific regions. The latter already requires something conceptual being added to the former and so the former is the real first point that needs accounting for. Similarly, in the first instance, we should not be thinking about the standard cause of the appearance of the impression as this will inevitably lead in the direction of Humean questions. The basic reason for that concerns the move, noted in the third movement, of minimizing the referential element when we become stuck on analysis of the occurrence in question in terms of a philosophical analysis that approximates to that of puzzlement of the ordinary perceiver.