Classification

Classification (Lat. classis, a class, probably from the root cal-, cla-, as in Gr. καλέω, clamor), a logical process, common to all the special sciences and to knowledge in general, consisting in the collection under a common name of a number of objects which are alike in one or more respects. The process consists in observing the objects and abstracting from their various qualities that characteristic which they have in common. This characteristic constitutes the definition of the “class” to which they are regarded as belonging. It is this process by which we arrive first at “species” and then at “genus,” i.e. at all scientific generalization. Individual things, regarded as such, constitute a mere aggregate, unconnected with one another, and so far unexplained; scientific knowledge consists in systematic classification. Thus if we observe the heavenly bodies individually we can state merely that they have been observed to have certain motions through the sky, that they are luminous, and the like. If, however, we compare them one with another, we discover that, whereas all partake in the general movement of the heavens, some have a movement of their own. Thus we arrive at a system of classification according to motion, by which fixed stars are differentiated from planets. A further classification according to other criteria gives us stars of the first magnitude and stars of the second magnitude, and so forth. We thus arrive at a systematic understanding expressed in laws by the application of which accurate forecasts of celestial phenomena can be made. Classification in the strict logical sense consists in discovering the casual interrelation of natural objects; it thus differs from what is often called “artificial” classification, which is the preparation, e.g. of statistics for particular purposes, administrative and the like.

Of the systems of classification adopted in physical science, only one requires treatment here, namely, the classification of the sciences as a whole, a problem which has from the time of Aristotle attracted considerable attention. Its object is to delimit the spheres of influence of the positive sciences and show how they are mutually related. Of such attempts three are specially noteworthy, those of Francis Bacon, Auguste Comte and Herbert Spencer.

Bacon’s classification is based on the subjective criterion of the various faculties which are specially concerned. He thus distinguished History (natural, civil, literary, ecclesiastical) as the province of memory, Philosophy (including Theology) as that of reason, and Poetry, Fables and the like, as that of imagination. This classification was made the basis of the Encyclopédie. Comte adopted an entirely different system based on an objective criterion. Having first enunciated the theory that all science passes through three stages, theological, metaphysical and positive, he neglects the two first, and divides the last according to the “things to be classified,” in view of their real affinity and natural connexions, into six, in order of decreasing generality and increasing complexity—mathematics, astronomy, physics, chemistry, physiology and biology (including psychology), and sociology. This he conceives to be not only the logical, but also the historical, order of development, from the abstract and purely deductive to the concrete and inductive. Sociology is thus the highest, most complex, and most positive of the sciences. Herbert Spencer, condemning this division as both incomplete and theoretically unsound, adopted a three-fold division into (1) abstract science (including logic and mathematics) dealing with the universal forms under which all knowledge of phenomena is possible, (2) abstract-concrete science (including mechanics, chemistry, physics), dealing with the elements of phenomena themselves, i.e. laws of forces as deducible from the persistence of forces, and (3) concrete science (e.g. astronomy, biology, sociology), dealing with “phenomena themselves in their totalities,” the universal laws of the continuous redistribution of Matter and Motion, Evolution and Dissolution.

Beside the above three systems several others deserve brief mention. In Greece at the dawn of systematic thought the physical sciences were few in number; none the less philosophers were not agreed as to their true relation. The Platonic school adopted a triple classification, physics, ethics and dialectics; Aristotle’s system was more complicated, nor do we know precisely how he subdivided his three main classes, theoretical, practical and poetical (i.e. technical, having to do with ποίησις, creative). The second class covered ethics and politics, the latter of which was often regarded by Aristotle as including ethics; the third includes the useful and the imitative sciences; the first includes metaphysics and physics. As regards pure logic Aristotle sometimes seems to include it with metaphysics and physics, sometimes to regard it as ancillary to all the sciences.

Thomas Hobbes (Leviathan) drew up an elaborate paradigm of the sciences, the first stage of which was a dichotomy into “Naturall Philosophy” (“consequences from the accidents of bodies naturall”) and “Politiques and Civill Philosophy” (“consequences from accidents of Politique bodies”). The former by successive subdivisions is reduced to eighteen special sciences; the latter is subdivided into the rights and duties of sovereign powers, and those of the subject.

Jeremy Bentham and A.M. Ampère both drew up elaborate systems based on the principle of dichotomy, and beginning from the distinction of mind and body. Bentham invented an artificial terminology which is rather curious than valuable. The science of the body was Somatology, that of the mind Pneumatology. The former include Posology (science of quantity, mathematics) and Poiology (science of quality); Posology includes Morphoscopic (geometry) and Alegomorphic(arithmetic). See further Bentham’s Chrestomathia and works quoted under Bentham, Jeremy.

Carl Wundt criticized most of these systems as taking too little account of the real facts, and preferred a classification based on the standpoint of the various sciences towards their subject-matter. His system may, therefore, be described as conceptional. It distinguishes philosophy, which deals with facts in their widest universal relations, from the special sciences, which consider facts in the light of a particular relation or set of relations.

All these systems have a certain value, and are interesting as throwing light on the views of those who invented them. It will be seen, however, that none can lay claim to unique validity. The fundamenta divisionis, though in themselves more or less logical, are quite arbitrarily chosen, generally as being germane to a preconceived philosophical or scientific theory.