THE CONCEPTS SERVE TO GROUP AND CLASSIFY.--But the somewhat complicated form of classification just described did not come to man ready-made. Someone had to _see_ the relationship existing among the myriads of animals of a certain class, and group these together under the general term _mammals_. Likewise with birds, reptiles, insects, and all the rest. In order to accomplish this, many individuals of each class had to be observed, the qualities common to all members of the class discriminated from those not common, and the common qualities retained as the measure by which to test the admission of other individuals into this class. The process of classification is made possible by what the psychologist calls the _concept_. The concept enables us to think _birds_ as well as bluebirds, robins, and wrens; it enables us to think _men_ as well as Tom, Dick, and Harry. In other words, _the concept lies at the bottom of all thinking which rises above the seeing of the simplest relations between immediately present objects_. GROWTH OF A CONCEPT.--We can perhaps best understand the nature of the concept if we watch its growth in the thinking of a child. Let us see how the child forms the concept _dog_, under which he is able finally to class the several hundred or the several thousand different dogs with which his thinking requires him to deal. The child's first acquaintance with a dog is, let us suppose, with a pet poodle, white in color, and named _Gyp_. At this stage in the child's experience, _dog_ and _Gyp_ are entirely synonymous, including Gyp's color, size, and all other qualities which the child has discovered. But now let him see another pet poodle which is like Gyp except that it is black in color. Here comes the first cleavage between _Gyp_ and _dog_ as synonyms: _dog_ no longer means white, but may mean _black_. Next let the child see a brown spaniel. Not only will white and black now no longer answer to _dog_, but the roly-poly poodle form also has been lost; for the spaniel is more slender. Let the child go on from this until he has seen many different dogs of all varieties: poodles, bulldogs, setters, shepherds, cockers, and a host of others. What has happened to his _dog_, which at the beginning meant the one particular little individual with which he played?