This is terribly hard, Thouless, I'm sorry. I have thought over all this for years. … It is now as if we had ploughed furrows in different parts of a field. There is a lot left to do. Judging from their writings, most contemporary analytic philosophers have not been persuaded that “the inverted spectrum problem” is – as Wittgenstein maintained – really a conceptual puzzle calling for dissolution, rather than a straight problem calling for a solution. In this paper, I (...) present Wittgenstein's view as clearly and persuasively as I can, contrasting it with the views of Sidney Shoemaker and Ned Block, two of his more prominent critics. I conclude with a look at Frank Jackson's well-known Knowledge Argument, which, if successful, would demonstrate the futility of looking for a physicalist solution to the inverted spectrum and related philosophical problems. My goal is to combat what I take to be the common and unfortunate failure – among both physicalistically inclined philosophers, including Shoemaker and Block, and anti-physicalists, such as Jackson – to appreciate the force of Wittgenstein's arguments. (shrink)