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, and the existence in the past of some special relation of the recognizer to the recognized, if only that of an observer.  In fact, it is evident that in this mode of recognition we have the transition from common perception to individual recollection.[8]

While we may thus distinguish different steps in the process of visual recognition, we may make a further distinction, marking off a passive and an active stage in the process.  The one may be called the stage of preperception, the other that of perception proper.[9] In the first the mind holds itself in a passive attitude, except in so far as the energies of external attention are involved.  The impression here awakens the mental images which answer to past experiences according to the well-known laws of association.  The interpretative image which is to transform the impression into a percept is now being formed by a mere process of suggestion.