In A scattering event we concluded that if the conditions stipulated by Rule B are met, then it is not the case that either alternative takes place. The question "Which outgoing particle is identical with which incoming particle?" is meaningless. The challenge, here as elsewhere, is to learn to think in ways that do not lead to meaningless questions.

Imagine that in front of you there are two exactly similar objects. Because they are in different places, they are different objects. But is the fact that they are in different places the sole reason why they are different objects? Or is there another reason?

"Ordinary" objects...

"Ordinary" objects occupy as much space as they do because atoms and molecules occupy as much space as they do. So how is it that a hydrogen atom in its ground state occupies a space roughly one tenth of a nanometer across?

The fundamental theoretical framework of contemporary physics is a probability algorithm (or else a set of rules for generating probability algorithms), and there is a notion that probabilities are inherently subjective. This notion is at the root of "epistemic" interpretations of the quantum formalism, according to which quantum theory concerns our knowledge of (or information about) the world, rather than the world itself. Under the influence of the new and fast growing field of quantum information, the slogan "quantum states are states of knowledge" (rather than states of Nature) has regained some of its original popularity. Yet quantum states are neither states of knowledge nor states of Nature. They are probability algorithms.

In the first two articles of this section we saw what an analysis of the way quantum mechanics assigns probabilities reveals about the "ultimate" constituents of matter. Namely, that there is only one ultimate constitutent.

In this article we shall see what an analysis of the way quantum mechanics assigns probabilities reveals about the nature of physical space.

Do the "ultimate constituents" of matter have a (pointlike) form? Or are they formless?

In this article (look here for an explanation of the title) I will argue that the spatial differentiation of the physical world is incomplete. It doesn't go all the way down. If in our minds we partition the world into smaller and smaller regions, there comes a point when there isn't any material object left for which these regions, or the corresponding distinctions, exist. Much the same is true of the temporal differentiation of the world.

Because spatial distinctions are relative and contingent, the distinctions we make between spatial regions have no reality per se. If they are to correspond to something in the real world, they must be realized (made real) by something as well as for something.

What can we say of a particle without internal structure, considered by itself, out of relation to anything else?

So the the number of "ultimate constituents of matter" equals one.

What shall we call this single ultimate constituent? I elect to call it "Reality" with an uppercase R. If you fancy another name, be my guest.