There has been much confusion in making classifications and some ingenious plans have been evolved for simplifying the process. That of Jevons is perhaps the simplest, when understood. This authority says: “All these difficulties are avoided in the _perfect logical method of dividing each Genus into two Species, and not more than two, so that one species possesses a particular quality, and the other does not_. Thus if I divide dwelling-houses into those which are made of brick and those which are not made of brick, I am perfectly safe and nobody can find fault with me…. Suppose, for instance, that I divide dwelling-houses as below:
Dwelling-House | –+——+——-+——-+——-+– | | | | | Brick Stone Earth Iron Wood
“The evident objection will at once be made, that houses may be built of other materials than those here specified. In Australia, houses are sometimes made of the bark of gum-trees; the Esquimaux live in snow houses; tents may be considered as canvas houses, and it is easy to conceive of houses made of terra-cotta, paper, straw, etc. All logical difficulties will, however, be avoided _if I never make more than two species at each step_, in the following way:–
Dwelling-House | +—-+—-+ | | Brick Not-Brick | +—-+—-+ | | Stone Not-Stone | +—-+—-+ | | Wooden Not-Wooden | +—-+—-+ | | Iron Not-Iron
“It is quite certain that I must in this division have left a place for every possible kind of house; for if a house is not made of brick, nor stone, nor wood, nor iron, it yet comes under the species at the right hand, which is not-iron, not-wooden, not-stone, and not-brick…. This manner of classifying things may seem to be inconvenient, but it is in reality the only logical way.”
The student will see that the process of Classification is two-fold. The first is by Analysis, in which the Genus is divided into Species by reason of _differences_. The second is by Synthesis, in which individuals are grouped into Species, and Species into the Genus, by reason of _resemblances_. Moreover, in building up general classes, which is known as Generalization, we must first _analyze_ the individual in order to ascertain its _qualities, attributes and properties_, and then _synthesize_ the individual with other individuals possessing like qualities, properties or attributes.
Brooks says of Generalization: “The mind now takes the materials that have been furnished and fashioned by comparison and analysis and unites them into one single mental product, giving us the general notion or concept. The mind, as it were, brings together these several attributes into a bunch or package and then ties a mental string around it, as we would bunch a lot of roses or cigars…. Generalization is an _ascending_ process. The broader concept is regarded as higher than the narrower concept; a concept is considered as higher than percept; a general idea stands above a particular idea. We thus go up from particulars to generals; from percepts to concepts; from lower concepts to higher concepts. Beginning down with particular objects, we rise from them to the general idea of their class. Having formed a number of lower classes, we compare them as we did individuals and generalize them into higher classes. We perform the same process with these higher classes and thus proceed until we are at last arrested in the highest class, that of Being. Having reached the pinnacle of Generalization, we may descend the ladder by reversing the process through which we ascend.”
A Concept, then, is seen to be a _general idea_. It is a general thought that embraces _all the individuals_ of its own class and has in it all that is common to its own class, while it resembles _no_ particular individual of its class in _all_ respects. Thus, a concept of _animal_ contains within itself the minor concepts of _all animals_ and the animal-quality of all animals–yet it differs from the _percept_ of any one particular animal and the minor concepts of minor classes of animals. Consequently a concept or general idea cannot be _imaged_ or mentally pictured. We may picture a percept of any particular thing, but we cannot picture a general idea or concept because the latter does not partake of the _particular_ qualities of any of its class, but embraces all the general qualities of the class. Try to picture the general idea, or concept, of Man. You will find that any attempt to do so will result in the production of merely _a man_–some particular man. If you give the picture dark hair, it will fail to include the light-haired men; if you give it white skin, it will slight the darker-skinned races. If you picture a stout man, the thin ones are neglected. And so on in every feature. It is impossible to form a correct general class picture unless we include every individual in it. The best we can do is to form a sort of _composite_ image, which at the best is in the nature of a symbol representative of the class–an ideal image to make easier the _idea_ of the general class or term.