PSYCHOLOGY, or the science of MIND, makes a wide transition, the widest that can be taken within the whole circle of the sciences, from the so-called material world, to the world of feeling, volition, and intellect. The main source of our knowledge of mind is self-consciousness; and it is only from the intimate connection of mind with a living organism that the subject is a proper sequel to biology. Not until lately has any insight into mind been obtained through the consideration of the physical organ—the brain; so that psychology might have been placed anywhere, but for another consideration that helps to determine the order of the sciences, viz., that the discipline, or method, of the simpler sciences is a preparation for the more abstruse. Mathematics and physics espe cially are an admirable training of the intellect for the studies connected with mind proper, although the laws of physics may not of themselves throw any direct light on the successions of thought and feeling. - These five sciences embrace all the fundamental laws of the world, and, if perfect, their application would suffice to account for the whole coarse of nature. To a person fully versed in them, no phenomenon of the explained universe can appear •strange; the. concrete sciences and the practical sciences contain nothing fundamentally new. They constitute a liberal scientific education. It is not uncommon, however, to rank SOCIOLOGY, or the laws of man in society, as a sixth primary science following on psychology, of which it is a special development.
Dr. Neil A rnott, in his work on Physics, first published in 1828, gave as the primary departments of nature—physics, chemistry, life, and mind which he would include the laws of society). lie did not discard mathematics, but looked upon it as a system of technical mensuration, created by the mind to facilitate the studs- of the other sciences, as well as the useful arts. The natural laws expressed by mathematics are few and sim ple, and the body of the science consists of a vast scheme of numerical computation, whose value appears in its applications to astronomy and the other physical sciences.
Auguste Comte, who, in his Coors de Philosophic Positire, went over the entire circle of the theoretical, abstract, or fundamental sciences, enumerated these us follows: mathe matics, astronomy, physics, chemistry, biology, sociology. lie thus detac:ies astronomy from physics, considering it as the abstract science that brings forward and works out the law of gravitation. He has no distinct science of psychology, an omission that has been generally condemned.
Mr. Herbert Spencer, in a tract on the Clas,qtation of the Sciences, takes exception to the scheme of Comte,Nand proposes a threefold division, according to the gradations of concreteness iu the subject-matter. The first group is termed ABSTRACT SCIENCE, and
treats of the Prins of phenomena detached from their embodiments. The most compre hensive forms are space and time; and the sciences corresponding are mathematics and logic. The second group is ABSTRACT-CONCRETE SCIENCE, or the phenomena of nature analyzed into their separate elements—gravity in the abstract, heat in the abstract—as in physics and chemistry. These are two of the fundamental sciences in every scheme, and they are called abstract-concrete by Mr. Spencer, in comparison with the foregoing class. The great principle of recent introductibn, termed the law of correlation, conservation, or, persistence of force, serves to connect physics with chemistry, and imparts to the two taken jointly a greater unity than belongs to physics singly. The third and last group is CONCRETE SCIENCE, or natural phenomena in their totalities, or as united iu actual things—astronomy, biology, psychology, sociology, geology, etc. Mr. John Stuart Mill, in all article in the 11estminster Review, April, 1865, has described Comte's scheme at length, and also criticised that of Spencer.
It may be held as generally admitted that mathematics, physics, chemistry, biology, and psychology, with or without sociology, are the sequence of the primary or funda mental sciences, and that the natural history group, from not containing any new laws of nature, are not fundamental. Astronomy, or the laws of the solar system, and of the other celestial bodies, might be called a natural history or concrete science, if we sup posed a prior abstract science that discussed the operation of gravity, together with the laws .e motion in bodies generally, or without special application to the existing solar and sidereal systems. The first book of Newton's Principia would be the abstract, the third book the concrete, form of the science.
The practical sciences do not admit of any regular classification. They are as numer ous as the separate ends of human life that can receive aid from science, or from knowl edge scientifically constituted. Connected with mind and society, we have ethics, logic, rhetoric, grain mar, philology, education, law, jurisprudence, politics, political economy, etc. In the manual and mechanical arts, there are navigation, practical mechanics, engineering civil and military, mining and metallurgy, chemistry applied to dyeing, bleaching, etc.
The medical department contains medicine, surgery, midwifery,. materia medico, medical jurisprudence. A science of living, or of the production of happiness by a skilled application of all existing resources, was greatly desideratecl by Plato, and would be the crowning practical science.