Knowing about the Actual World
What I am ultimately interested is the nature of the actual world. The actual — rather than just the possible — because ‘all my stuff is there’ (to quote Dr. Colossus in The Simpsons). Philosophical zombies, life after death, the extinction of the human race by asteroid, punctuated equilibrium, that my brother ate my easter egg without telling me — all of these are possible, at least in the broadest sense. I am interested in what is possible insofar as it tells me something about what is actual, e.g., as merely possible philosophical zombies are alleged to do. That they are actual is what is ultimately important (in my view, at least — there may be other views).
The interest in the actual world leads to interest in the following question as well: how can we know about the actual world?
One answer looks wrong: we can know about it through thought alone. We get at the actual world through merely thinking about it. The problem is this: we can think about anything at all. As Anthony Kenny puts it “[i]f we are to say that there is a formal object of thought we must say that it is: anything whatever“. Although he refers to a formal object, and so may mean some abstracted logical object of thought, I take it also to mean that it is possible to think of anything. The only restrictions are those arising from the conditions of thought, e.g., perhaps, that whatever we think about it is coherent.
It seems right that this ‘anything’ includes what is possible. Yet, just because something can be thought of, and just because it is possible, does not mean that it is actual. We can conceive of teleporting cats; but teleporting cats are not actual. That I got a degree in Astrophysics in Manchester is possible (I got into the programme many years ago) but not actual (I went to Cork instead). What you can think of, and what is possible, is too broad to pick out what is in the actual world while leaving what is merely possible aside.
So what can we use to pick out what is in the actual world? A natural-seeming answer is: experience — and more specifically, perceptual experience. That is: Perceptual experience shows or presents the actual world to you.
However, there are two possible problems with taking perceptual experience as it stands:
A. Incompleteness: Perceptual Experience does not show you everything about the world.
B. Illusion/Hallucination: There are reasons to doubt even what Perceptual Experience does show you.
I think that incompleteness (‘A’) not the worst of problems. Given this incompleteness or limitation of experience, we at least know about some of the actual world. We can at least, from our experience, get a minimal account of the actual world from which we can build.
I think illusion/hallucination (‘A’) is close to the worst epistemological problem.
Next (page 3 of 5 below): Why illusion?