In the first chapter of Williamson’s book, he spends a lot of time on McDowell’s argument that non-psychological sense is not only a small fraction of reality. The argument goes:
(i) There is no gap between what one thinks and the sort of thing that can be the case.
(ii) What one thinks is what is the case.
(iii) Since (i) and (ii) then (iv)
(iv) There is no gap between thought and the world
Williamson goes on to state that McDowell’s argument requires the premise that ‘everything (object, property, relation, state of affairs, …) is thinkable. He also states that to allow this premise as true is ‘highly contentious’ for the reason that reality could contain elusive objects, incapable of being individually thought of. His example for this is as follows:
‘Can we be sure that ordinary material objects do not consist of clouds of elusive sub-sub-atomic particles? We might know them by their collective effects while unable to think of any single one of them.’
Williamson goes on to state that because we cannot rule out the possibility of elusive objects McDowell cannot have the premise ‘everything is thinkable’.
The question then arises is it necessary that for something to be thought of we must think of the individual particles that constitute it? This might imply that to truly think of my dog Arthur I must not only think of him as a black lab with white feet I must think of all the physiological systems that contribute to his being. That to truly think of anything we must be sure to think of the most basic molecular structure of that thing. Surly we can not claim that this is the case when we think about all things. Is it enough to simply state that we are aware of the possibility of elusive objects and can think of them in this non-specific way? Williamson doesn’t seem the think so. To me it seems that there is a need for a definition of what it means to be ‘thinkable’ if we want to decipher what is and what isn’t.
I hope this kind of makes sense, I welcome anyone's thoughts.