s of the characters of things perceived. Accordingly to affirm
that the cook is a certain dance of molecules and electrons is merely to
affirm that the things about her which are perceivable have certain
characters. The situations of the perceived manifestations of her bodily
presence have only a very general relation to the situations of the
molecules, to be determined by discussion of the circumstances of
perception.

In discussing the relations of situation in particular and of ingression
in general, the first requisite is to note that objects are of radically
different types. For each type 'situation' and 'ingression' have their
own special meanings which are different from their meanings for other
types, though connexions can be pointed out. It is necessary therefore
in discussing them to determine what type of objects are under
consideration. There are, I think, an indefinite number of types of
objects. Happily we need not think of them all. The idea of situation
has its peculiar importance in reference to three types of objects which
I call sense-objects, perceptual objects and scientific objects. The
suitability of these names for the three types is of minor importance,
so long as I can succeed in explaining what I mean by them.

These three types form an ascending hierarchy, of which each member
presupposes the type below. The base of the hierarchy is formed by the
sense-objects. These objects do not presuppose any other type of
objects. A sense-object is a factor of nature posited by sense-awareness
which (i), in that it is an object, does not share in the passage of
nature and (ii) is not a relation between other factors of nature. It
will of course be a relatum in relations which also implicate other
factors of nature. But it is always a relatum and never the relation
itself. Examples of sense-objects are a particular sort of colour, say
Cambridge blue, or a particular sort of sound, or a particular sort of
smell, or a particular sort of feeling. I am not talking of a particular
patch of blue as seen during a particular second of time at a definite
date. Such a patch is an event where Cambridge blue is situated.
Similarly I am not talking of any particular concert-room as filled with
the note. I mean the note itself and not the patch of volume filled by
the sound for a tenth of a second. It is natural for us to think of the
note in itself, but in the case of colour we are apt to think of it
merely as a prop