Chapter 3: Adventures with a Cosmoscope

To argue for scrutability theses, as I do in this chapter and the next, we first need a potential scrutability base. I will start with a reasonably generous base. Later (in chapters 6 and 7), I will consider whether it needs to be augmented and whether it can be narrowed down. In the Aufbau, Carnap’s main base was a phenomenal base, consisting just of logical expressions plus an expression for phenomenal similarity (similarity of conscious experiences). This base was rejected by Goodman on the grounds that it does not definitionally entail all truths about specific phenomenal qualities of experience, and by Quine on the grounds that it does not definitionally entail all physical truths about the external world. Carnap suggests in the Aufbau that he might instead have used a physical base. This base would have avoided Goodman’s and Quine’s problems, which are specific to Carnap’s phenomenal base, but it would have had other problems. It is arguable that just as physical truths are not definitionally entailed by phenomenal truths, phenomenal truths (‘Someone is conscious’, ‘Suchand-such is what it is like to see red’) are not definitionally entailed by physical truths, at least if definitions are required to be a priori. This is often held to be one of the main morals of Frank Jackson’s thought-experiment concerning Mary, the neuroscientist who knows all the physical truths about color processing but still does not know what it is like to see red. It is at least arguable that no amount of a priori reasoning can lead Mary from the physical truths to full knowledge of the phenomenal truths. There are a couple of other immediate problems for a physical base. First, there is good reason to believe that some indexical truths (‘I am David Chalmers’, ‘It is now 3am’) are not scrutable from objective physical truths alone. Someone might in principle know all the objective physical truths about the world and be a perfect a priori reasoner without being in a position to know these indexical truths. Second, there is good reason to believe that various negative truths (‘There is