elonging to some
athlete. The coat itself is a perceptual object and its situation is not
what I am talking about. We are talking of someone's definite
sense-awareness of Cambridge blue as situated in some event of nature.
He may be looking at the coat directly. He then sees Cambridge blue as
situated practically in the same event as the coat at that instant. It
is true that the blue which he sees is due to light which left the coat
some inconceivably small fraction of a second before. This difference
would be important if he were looking at a star whose colour was
Cambridge blue. The star might have ceased to exist days ago, or even
years ago. The situation of the blue will not then be very intimately
connected with the situation (in another sense of 'situation') of any
perceptual object. This disconnexion of the situation of the blue and
the situation of some associated perceptual object does not require a
star for its exemplification. Any looking glass will suffice. Look at
the coat through a looking glass. Then blue is seen as situated behind
the mirror. The event which is its situation depends upon the position
of the observer.

The sense-awareness of the blue as situated in a certain event which I
call the situation, is thus exhibited as the sense-awareness of a
relation between the blue, the percipient event of the observer, the
situation, and intervening events. All nature is in fact required,
though only certain intervening events require their characters to be of
certain definite sorts. The ingression of blue into the events of nature
is thus exhibited as systematically correlated. The awareness of the
observer depends on the position of the percipient event in this
systematic correlation. I will use the term 'ingression into nature' for
this systematic correlation of the blue with nature. Thus the ingression
of blue into any definite event is a part statement of the fact of the
ingression of blue into nature.

In respect to the ingression of blue into nature events may be roughly
put into four classes which overlap and are not very clearly separated.
These classes are (i) the percipient events, (ii) the situations, (iii)
the active conditioning events, (iv) the passive conditioning events. To
understand this classification of events in the general fact of the
ingression of blue into nature, let us confine attention to one
situation for one percipient event and to the consequent _roles_ of the
conditioning e