orming
a moment is a {sigma}-antiprime, where {sigma} has this special meaning,
and (ii) that we have excluded from membership of moments abstractive
sets of durations which all have one common boundary, either the initial
boundary or the final boundary. We thus exclude special cases which are
apt to confuse general reasoning. The new definition of a moment, which
supersedes our previous definition, is (by the aid of the notion of
antiprimes) the more precisely drawn of the two, and the more useful.

The particular condition which '{sigma}' stood for in the definition of
moments included something additional to anything which can be derived
from the bare notion of extension. A duration exhibits for thought a
totality. The notion of totality is something beyond that of extension,
though the two are interwoven in the notion of a duration.

In the same way the particular condition '{sigma}' required for the
definition of an event-particle must be looked for beyond the mere
notion of extension. The same remark is also true of the particular
conditions requisite for the other spatial elements. This additional
notion is obtained by distinguishing between the notion of 'position'
and the notion of convergence to an ideal zero of extension as exhibited
by an abstractive set of events.

In order to understand this distinction consider a point of the
instantaneous space which we conceive as apparent to us in an almost
instantaneous glance. This point is an event-particle. It has two
aspects. In one aspect it is there, where it is. This is its position in
the space. In another aspect it is got at by ignoring the circumambient
space, and by concentrating attention on the smaller and smaller set of
events which approximate to it. This is its extrinsic character. Thus a
point has three characters, namely, its position in the whole
instantaneous space, its extrinsic character, and its intrinsic
character. The same is true of any other spatial element. For example an
instantaneous volume in instantaneous space has three characters,
namely, its position, its extrinsic character as a group of abstractive
sets, and its intrinsic character which is the limit of natural
properties which is indicated by any one of these abstractive sets.

Before we can talk about position in instantaneous space, we must
evidently be quite clear as to what we mean by instantaneous space in
itself. Instantaneous space must be looked for as a character of a