are
different types of objects, and statements which are true of objects of
one type are not in general true of objects of other types. The objects
with which we are here concerned in the formulation of physical laws are
material objects, such as bits of matter, molecules and electrons. An
object of one of these types has relations to events other than those
belonging to the stream of its situations. The fact of its situations
within this stream has impressed on all other events certain
modifications of their characters. In truth the object in its
completeness may be conceived as a specific set of correlated
modifications of the characters of all events, with the property that
these modifications attain to a certain focal property for those events
which belong to the stream of its situations. The total assemblage of
the modifications of the characters of events due to the existence of an
object in a stream of situations is what I call the 'physical field' due
to the object. But the object cannot really be separated from its field.
The object is in fact nothing else than the systematically adjusted set
of modifications of the field. The conventional limitation of the object
to the focal stream of events in which it is said to be 'situated' is
convenient for some purposes, but it obscures the ultimate fact of
nature. From this point of view the antithesis between action at a
distance and action by transmission is meaningless. The doctrine of this
paragraph is nothing else than another way of expressing the
unresolvable multiple relation of an object to events.

A complete time-system is formed by any one family of parallel
durations. Two durations are parallel if either (i) one includes the
other, or (ii) they overlap so as to include a third duration common to
both, or (iii) are entirely separate. The excluded case is that of two
durations overlapping so as to include in common an aggregate of finite
events but including in common no other complete duration. The
recognition of the fact of an indefinite number of families of parallel
durations is what differentiates the concept of nature here put forward
from the older orthodox concept of the essentially unique time-systems.
Its divergence from Einstein's concept of nature will be briefly
indicated later.

The instantaneous spaces of a given time-system are the ideal
(non-existent) durations of zero temporal thickness indicated by routes
of approximation along series f