itself, especially in the case of living beings, there are
varying effects of illumination, of position in relation to the eye, of
distance, and so on, which very distinctly affect the visual impression
at different times. Yet the fact of our instantly recognizing a familiar
object in spite of these fluctuations of appearance, proves that we are
able to overlook a very considerable amount of diversity when a certain
amount of likeness is present.

It is further to be observed that in these last stages of perception we
approach the boundary line between perception and inference. To
recognize an object as one of a class is often a matter of conscious
reflection and judgment, even when the class is constituted by obvious
material qualities which the senses may be supposed to apprehend
immediately. Still more clearly does perception pass into inference when
the class is constituted by less obvious qualities, which require a
careful and prolonged process of recollection, discrimination, and
comparison, for their recognition. Thus, to recognize a man by certain
marks of gesture and manner as a military man or a Frenchman, though
popularly called a perception, is much more of an unfolded process of
conscious inference. And what applies to specific recognition applies
still more forcibly to individual recognition, which is often a matter
of very delicate conscious comparison and judgment. To say where the
line should be drawn here between perception and observation on the one
hand, and inference on the other, is clearly impossible. Our whole study
of the illusions of perception will serve to show that the one shades
off into the other too gradually to allow of our drawing a hard and fast
line between them.

Finally, it is to be noted that these last stages of perception bring us
near the boundary line which separates objective experience as common
and universal, and subjective or variable experience as confined to one
or to a few. In the bringing of the object under a certain class of
objects there is clearly room for greater variety of individual
perception. For example, the ability to recognize a man as a Frenchman
turns on a special kind of previous experience. And this transition from
the common or universal to the individual experience is seen yet more
plainly in the case of individual recognition. To identify an object,
say a particular person, commonly presupposes some previous experience
or knowledge of this object, a