(Of course sensory perceptions are obviously subject to logical constraints in the ordinary sense that, e.g., a sensory perception cannot be and not be at the same time and in the same respect; but beliefs and actions seem subject to logical constraints in the stronger sense of having conceptually structured content, and this is what sensory perceptions might seem to lack.)
But how can this be so, McDowell asks in his 1994 book Mind and World, if perceptual experience is to be the basis of our judgments? I have a perceptual experience of, or as of, a tree in front of me, and so I form the judgment “There is a tree in front of me.” The judgment has conceptual articulation, logical form – but what about the perceptual experience? If it lacks conceptual articulation, then how can it be the basis for my conceptually articulated judgment? Perhaps it could be the cause of my judgment, but we ordinarily think of perceptual experiences as actually justifying our judgments, and merely causing a judgment does not justify it – except perhaps in the weak sense of exculpating it, of making us blameless for so judging, but not in the stronger sense of providing reasons for it:
[W]e must not picture an outer boundary around the sphere of the conceptual, with a reality outside the boundary impinging inward on the system. Any impingements across such an outer boundary could only be causal, and not rational ....37
If perceptual experiences are supposed to rationalise the judgments we base on them, then they can be no less conceptually articulated than the judgments themselves; otherwise we should be in the position of, in effect, deriving propositional conclusions from non-propositional premises. Hence logical form cannot be a special privilege of an elite subset of inner-realm items, the conceptual ones; it must apply to them all.
But it is not just inner-realm items like perceptual experiences that must be conceptually articulated in order for our judgments to be rationalised; outer-realm items must be so as well. For our judgments and experiences alike have
37 John McDowell, Mind and World (Harvard University Press, 1996), p. 34.
R. T. Long – Wittgenstein, Praxeology, and Frege’s Three Realms – p. 26