this aspect of it also
seems to extend beyond nature to mind.

It is important to distinguish simultaneity from instantaneousness. I
lay no stress on the mere current usage of the two terms. There are two
concepts which I want to distinguish, and one I call simultaneity and
the other instantaneousness. I hope that the words are judiciously
chosen; but it really does not matter so long as I succeed in explaining
my meaning. Simultaneity is the property of a group of natural elements
which in some sense are components of a duration. A duration can be all
nature present as the immediate fact posited by sense-awareness. A
duration retains within itself the passage of nature. There are within
it antecedents and consequents which are also durations which may be the
complete specious presents of quicker consciousnesses. In other words a
duration retains temporal thickness. Any concept of all nature as
immediately known is always a concept of some duration though it may be
enlarged in its temporal thickness beyond the possible specious present
of any being known to us as existing within nature. Thus simultaneity is
an ultimate factor in nature, immediate for sense-awareness.

Instantaneousness is a complex logical concept of a procedure in thought
by which constructed logical entities are produced for the sake of the
simple expression in thought of properties of nature. Instantaneousness
is the concept of all nature at an instant, where an instant is
conceived as deprived of all temporal extension. For example we conceive
of the distribution of matter in space at an instant. This is a very
useful concept in science especially in applied mathematics; but it is a
very complex idea so far as concerns its connexions with the immediate
facts of sense-awareness. There is no such thing as nature at an instant
posited by sense-awareness. What sense-awareness delivers over for
knowledge is nature through a period. Accordingly nature at an instant,
since it is not itself a natural entity, must be defined in terms of
genuine natural entities. Unless we do so, our science, which employs
the concept of instantaneous nature, must abandon all claim to be
founded upon observation.

I will use the term 'moment' to mean 'all nature at an instant.' A
moment, in the sense in which the term is here used, has no temporal
extension, and is in this respect to be contrasted with a duration which
has such extension. What is directly yielded to our kn