EXPLANATION (Lat. explanatio, from ex planare, to explain. from ex, out --F. planare, to level, from planes, plain). In science, the giving of a complete description of some object or event. In certain cases this end is attained by the sub sumption of the phenomenon to a general law, as when a physical fact is brought under one or other of the general laws of mechanics. The law, in such instances, is mathematically exact; it sums up in shorthand all the conditions under which the phenomenon in question appears; it sets the phenomenon in its right place within the causal nexus of the material universe. In fields of science that are less 'exact' than physics, such as hiology and psychology, explanation takes on a different form. The laws of these sciences are, for the most part, hypothetical generalizations or supplementings of the facts more or less hypothet ical in character, rather than shorthand formula derived from the facts themselves; so that sub sumption to them, while it may help to confirm a theory or to classify an otherwise hetero geneous subject-matter, does not constitute ex planation. Nothing is more erroneous than the popular belief that a given fact is adequately explained when it is referred to a 'principle' of heredity or of memory. Explanation consists rather in an accurate description of the fact as observed, together with a statement, as full as the circumstances permit, of the proximate con ditions under which it appears. Thus a fact of
mind, a complex mental process, is explained when we have (1) analyzed it into its elements, sensation and affection, and (2) referred these constituent processes to their proximate physical conditions in the cerebral cortex. To explain, e.g. an impulse as a 'manifestation of our active nature' or of a `faculty of or to account for the rise of an idea in consciousness by a 'law of telepathy.' is to interpret. a fact, a scientific datum, which can be known, in terms of the less known and hypothetical. Misunderstand ings of this sort have recently called forth emphatic protest from men of eminence in scien tific inquiry. 'The business of all science is the description of facts'; and when a scientific 'theory' goes beyond the specification of the conditions under which the facts are observable, it ceases to be an aid to thought and becomes a positive hindrance. Consult: lifllpe, Outlines of Psychology (Eng. trans. London, 1895) : id., Introduction to Philosophy (Eng. trans. New York, 1897) : Mach, Contributions to the Analy sis of the Sensations(Eng. trans. Chicago, 1897) ; Popular Scientific Lectures (Eng. trans. Chicago, 1895 ) .