The first thing I’d like to note—by way of protest—is that these issues are typically treated by scholars as fringe issues: as if they were ornaments, somewhat inessential, somewhat on the edges of the more serious philosophical investigations, and in general as matters one should deal with in one’s spare time. Normally, I imagine the thought goes, language takes us where we need to go. Normally things work. Philosophy tracks thought and language—tracks them when they work. The interest in those fringe topics only blossoms when things break—when we enter those twilight zones of thought where language fails us. – The thought here is deeply confused. It imagines that there is anywhere for philosophy to be except in the fringes of thought and language. It imagines that philosophy can be anything but a twilight zone investigation. Treating those fringe topics in this manner is not only a misunderstanding of them; it also tells of a misunderstanding of what, as opposed to those topics, is taken to lie at the heart of philosophy, like the problem of other minds, skepticism of the external world, the mind body problem, questions about the reality of the good and the beautiful, and so on.
For what is it that we take to be the similarity between those fringe topics mentioned in the first paragraph? – I suspect that one of the first things that come to mind here is that dealing with those topics involves flirtation with nonsense. There is a strong resemblance between the logical problematic that characterizes those topics. Perhaps the word ‘logical’ should here give way to the word ‘grammatical,’ since the different kinds of uses of language involved in those cases—the use of words in absolute and in secondary sense, for instance—are all implicated by a similar kind of logical peculiarity, a peculiarity internal to which is that perfectly capable speakers may take those uses for nonsense.
It can indeed be said that the affinity between those cases is connected to the fact that they all involve us in similar relationships with nonsense. But if that is the case, then those topics lie very much at the heart of philosophy. For what is philosophy all about? Pick any philosophical topic. The question of nonsensicality is already there. The wrestling with nonsense is internal—part of the very foundation of the discussion. Philosophy is a constant wrestling with nonsense. Insofar as philosophy is indeed a battle against the bewitchment of our intelligence by means of our language, treating those fringe issues as if they were just curiosities oddities and eccentricities is missing the point of philosophy as a whole.
Again, philosophy investigates the foundations of our structures of meaning. Studying this is constantly remembering the possibility of their absence. Philosophy is the investigation of those moments in which lines of thoughts are derailed into incoherence (in discussions about God, sensations, the past, fictional characters, the good, color, numbers, free will, and so on). We do philosophy just because we are intrigued—made curious, frightened—by those moments in life in which we start treading on, and possibly building relationships with, nonsense. The investigation of those fringe phenomena is therefore simply the investigation of the different shapes that wrestling with nonsense takes in different cases—of the different shapes of philosophy itself.