Daniel: Yes and no. Have you read Stewart Shapiro's book, "Thinking About Mathematics"?
David: Of course I have. That's an excellent book. The only thing that I don't like about it is that there's no section about me.
Daniel: Remember how Shapiro distinguishes between two kinds of mathematical realism?
David: Yes, "ontological realism" and "truth-value realism". An "ontological realist" believes that numbers exist as objects, whereas a "truth-value realist" believes that mathematical statements are true, but that the numbers and other mathematical things do not really exist as objects.
Daniel: I'm a truth-value realist.
David: About what? About math?
Daniel: About life, the universe, and everything. About matter, you could say. That's why I wouldn't call myself an idealist, even though I strongly sympathize with the subjective idealist position.
David: You're suggesting that matter is not ontologically real, but it's real in truth-value? How could that be? If matter is not ontologically real, how can it be anything?
Daniel: I mean that atoms, molecules, stars, plants, animals, building blocks, tennis balls etc. may not be ontologically real, but statements made about them are true (or, sometimes false, according to the common-sense criteria for these things). You just need to do a little bit of reinterpretation.
David: Sure, that's what you were saying in your last blog post, that science can be philosophically justified if you reinterpret it. But why is that not subjective idealism?
Daniel: Can you stand on the pavement for a minute?
David: Another experiment?
Daniel: Now take this wooden block.
David: Wow! That's beautiful! Where did you get that?
Daniel: At the toy store on Rothschild, if you can believe that. Now put it down on the pavement and roll it.
David tries to roll the block.
Daniel: How does it roll?
David: Not very well. It doesn't really roll at all.
Daniel: Why not?
David: I don't know. Because it's a block, I guess.
Daniel: Right, it's shaped like a cube. Here's another one from the same set. Stack it on top of the first one.
David: These things are really spectacular. How many of them do you have?
Daniel: There were eleven in the set, but I only brought two of them. Now give me back the blocks and come back to the sidewalk.
David: Are we done with the experiment?
Daniel: Here's the tennis ball from my last post. Roll this. And here's another tennis ball. Can you stack it on top of the first one?
David: No, these tennis balls don't stack...
Daniel: Very good, I'll take back the balls.
David: Anything else? Pyramids?
Daniel: No, that's it. Now, let's talk about what just happened. You were on the pavement for a few minutes, then you were on the sidewalk.
David: I don't know, maybe I wasn't.
Daniel: But you remember being on the pavement then on the sidewalk, and playing with blocks and tennis balls.
David: Yes, I remember it well.
Daniel: We could talk about two memory streams, one composed of ordered, contiguous remembered moments on the pavement, and one composed of moments on the sidewalk.
David: That sounds like a good way of thinking about it.
Daniel: What is the difference between those two memory streams?
David: I don't know. There are a lot of differences. What are you getting at?
Daniel: In each stream, you were playing with two objects, but on the pavement you couldn't roll the objects, they stacked well, and they had straight edges. All of those properties are properties of the memory stream, not a quality of any single moment of memory.
David: I don't know, maybe I wasn't.
Daniel: But you remember being on the pavement then on the sidewalk, and playing with blocks and tennis balls.
David: Yes, I remember it well.
Daniel: We could talk about two memory streams, one composed of ordered, contiguous remembered moments on the pavement, and one composed of moments on the sidewalk.
David: That sounds like a good way of thinking about it.
Daniel: What is the difference between those two memory streams?
David: I don't know. There are a lot of differences. What are you getting at?
Daniel: In each stream, you were playing with two objects, but on the pavement you couldn't roll the objects, they stacked well, and they had straight edges. All of those properties are properties of the memory stream, not a quality of any single moment of memory.
David: Properties of the memory stream. OK, that makes sense.
Daniel: So you generalize over these disparate properties of the memory stream with a single property, and say that on the pavement you were playing with balls.
David: But the balls would only be a property of the memory stream, not objects with a distinct ontological existence.
Daniel: That's exactly what I'm saying. Matter is a property of memory streams. Or, any material object is a property of a memory stream.
David: That kind of makes sense, but weren't you going to distance yourself from subjective idealism? It still sounds like idealism to me.
Daniel: I think that our common sense notions of matter are correct, they just need a little bit of reinterpretation.
David: So you're saying that our common sense notions of matter are correct in the sense that they're incorrect.
Daniel: No. Our common sense notions of matter are correct in the particulars. The necessary reinterpretation is in the realm of the extremely general.
David: But you're not saying something that a subjective idealist would disagree with. At best, you're providing better tools of analysis.
Daniel: So call it analytical philosophy. The bottom line is this: George always says that matter is a delusion. I say that, when correctly viewed, matter is a property of a memory stream. Matter isn't a delusion, it's an illusion. It's the perfect illusion. And the perfect illusion is equivalent to reality.
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