But it should be firmly kept in mind that, fundamentally, science is one, having in all its branches but one aim and object, viz., the ascertainment and demonstration of the exact truth of things as far as human capacities are able to reveal and comprehend such truth, and also but one method of procedure, which is the method of common sense trained to the utmost attainable exactitude in observation and the greatest possible clearness and precision of reasoning. Science properly so-called confines itself to things that are subject to observation by the senses and to verification by repeated observation and experiment, while its reasonings and predictions are based entirely upon the unvarying sequence of the phenomena of nature, as they display themselves before us.
Science is just as one and inseparable as life, or as an organic being, and its divisions no more imply lack of unity than do the various organs and limbs of an animal, or a tree, or the different structural parts of a building. Astronomy is not entirely independent of geology, nor geology of botany, nor botany of chemistry, nor any of these of physics, nor physics of electricity and magnetism, nor the last of physiology and medicine. Accordingly the question where to begin in studying science is not one that can be answered in the same way for everybody. But the spirit is the same in all the branches.
Perhaps the best general indication of the order in which a person who has no predilection for any one branch of science should take up the various parts is afforded by their historic development. This was a result of the natural reaction of man's mind to its surroundings. The things nearest to him, and most immediately important, first attracted his attention. The broadest division would be into the science of things on the earth's surface; the science of things above the earth, in the air and the sky; and the science of things within the earth, concealed from immediate view.
If we take these in their order they naturally subdivide themselves as follows:
1—Things on the Earth—Explained by
(a) Anthropology, the Science of Man and His Ancestors, treating of his nature, origin, development, division into races and tribes, society, industry, etc.
(b) Zoölogy, the Science of Animal Life, treating of the "lower animals," and of animal life in general as distinguished from the kingdom of the plants, although the related science of biology deals with both plants and animals, its special subject being the phenomena of life in its widest sense.
(c) Botany, the Science of Plant Life.
(d) Geography, combined with Physiography, the Science of the Face, or Superficies, of the Earth, dealing with lands and seas, rivers and mountains, political divisions, etc. This is covered in our series by the volume on Physiography.