W: You don’t know anything about the world until you test.
J: Doesn’t that have the same problem all Logical Positivism has? The statement itself is untestable.
W: Not at all: it’s not a statement about the world, but about our knowledge of it. It is a logical statement, taken in the broad sense of “logic”. It’s not a statement about the world except so far as it relates to our knowing it. Therefore there is no problem of “how is that statement testable?”
J: So there are logical statements, and statements about the world?
J: And the latter must be testable?
W: We must be able at least to relate the statement to something testable.
J: So what has come to be called “a philosophy of nature” can’t tell us any facts about the world then.
W: That’s right. This idea that you could just think real hard about time and figure out that it was “the number of motion according to in front of and behind” or that everything that moves must be an extended body (which is crucial for Aristotle’s proof for the existence of a Prime Mover), or that things must be made out of two principles (matter and form) is all unknowable stuff. The sort of reasoning that comes to such conclusions isn’t capable of giving us real facts about the world. And all the claims that I’ve just made are logical claims, not claims about the world, including this one.
J: And how did you figure this all out?
W: Not by science, but by the logical reflection on it. Look at it this way: lets say you are Aristotle, and you’ve just come up with a spectacular argument, absolutely air tight, that whatever moves must be a body. He’s right, for example, that if something had no extension, and still went from here to there, then it would have to have moved even though it never was moving. But what if you discover that there is some particle that clearly moves from here to there, but has a mass of zero? What then? Our explanation of the world has to explain our experience, and if the best explanation of our experience is that things with no extension are moving, then so much for the linguistic inconvenience about things having moved without moving.
J: So Aristotle’s argument is all about words? Why is his not the reality and the scientist’s just words? Is this where the test comes in?
W: Yes. The test is what makes the difference between mere linguistic tricks and statements about the world. If you’re talking about the world, I’ll listen; if you’re talking about words, then I’m going.
J: So experience is always capable of critiquing our experience. We can never know a priori what we will discover about the world. If we have no way of letting experience critique our ideas, then either our ideas are not about the world.
W: Yes, and the test is nothing but finding a way to open our idea to the critique of experience. Get rid of this, and you don’t even have any knowledge of the world. It is no longer an investigation of experience.
J: And what about a claim like this: motion is not a fish. Is this the sort of thing that needs to relate to a test?
W: I don’t suppose so, but this sort of negative claim is not exactly a claim about the world.
J: I don’t see why not – and at any rate is seems to be based on some sort of positive awareness of things: motion is something things have, or some sort of property while a fish is not.
W: But this is a very minimal knowledge of things. Motion is a property. Big deal.
J: But we could develop this idea, I suppose. Couldn’t we ask “what sort of property”?