many sorts of objects. For example, the colour
green is an object according to the above definition. It is the purpose
of science to trace the laws which govern the appearance of objects in
the various events in which they are found to be situated. For this
purpose we can mainly concentrate on two types of objects, which I will
call material physical objects and scientific objects. A material
physical object is an ordinary bit of matter, Cleopatra's Needle for
example. This is a much more complicated type of object than a mere
colour, such as the colour of the Needle. I call these simple objects,
such as colours or sounds, sense-objects. An artist will train himself
to attend more particularly to sense-objects where the ordinary person
attends normally to material objects. Thus if you were walking with an
artist, when you said 'There's Cleopatra's Needle,' perhaps he
simultaneously exclaimed 'There's a nice bit of colour.' Yet you were
both expressing your recognition of different component characters of
the same event. But in science we have found out that when we know all
about the adventures amid events of material physical objects and of
scientific objects we have most of the relevant information which will
enable us to predict the conditions under which we shall perceive
sense-objects in specific situations. For example, when we know that
there is a blazing fire (_i.e._ material and scientific objects
undergoing various exciting adventures amid events) and opposite to it a
mirror (which is another material object) and the positions of a man's
face and eyes gazing into the mirror, we know that he can perceive the
redness of the flame situated in an event behind the mirror--thus, to a
large extent, the appearance of sense-objects is conditioned by the
adventures of material objects. The analysis of these adventures makes
us aware of another character of events, namely their characters as
fields of activity which determine the subsequent events to which they
will pass on the objects situated in them. We express these fields of
activity in terms of gravitational, electromagnetic, or chemical forces
and attractions. But the exact expression of the nature of these fields
of activity forces us intellectually to acknowledge a less obvious type
of objects as situated in events. I mean molecules and electrons. These
objects are not recognised in isolation. We cannot well miss Cleopatra's
Needle, if we are in its neighbourhood