cient to have changed his opinion; for metaphysical conceptions, like spiritual substances, yield to no carnal weapons.
Herein consists the great danger in the introduction of abstractions into scientific discussions. Let them once be assumed to have an existence outside the concretes from which they are formed—and the tendency with many is to consider them in this light—and no argument, based upon the observation of phenomena, is sufficient to overthrow them. It can not be too strongly impressed upon the minds of all that science has nothing to do with such conceptions. As science consists in the observation of phenomena and the deduction of the laws of their orderly occurrence, and as scientific hypothesis consists in the prediction of the order of the future occurrence of phenomena and the linking together of diverse phenomena under an assumed order, we see that there is no place where these realistic conceptions can enter. Their sphere, if anywhere, is in metaphysics and theology. Scientists should exercise the utmost care not to misapprehend their own terms, and should then compel acquiescence in the meaning they give to them. Looseness in the use of words is one cause of the indefiniteness that pervades the controversy between the scientists and the theologians.
Force, cause, matter, and science itself are abstract terms, and when analyzed into their concretes will assume a meaning very different from that often given them. All that we scientifically know of force is, that it connotes the presence of motion (i. e., things moving) under different conditions. These we separate into actual and potential motion, and the cause of the motion into actual and potential force or energy. Here the necessity of the use of these abstract terms is at once apparent, as we can scarcely make an assertion without employing them. Cause, as in the above-mentioned case of law, is simply the preceding conditions of any phenomenon, and in the absence of which, as far as we know, it can not occur. Likewise matter, the most "real" of all abstractions, is, scientifically speaking, merely the symbol of a congeries of the phenomena of extension; and Professor Tyndall was speaking entirely within scientific bounds when he said he discerned in it the promise and potency of all forms of life. This did not in the least prejudice the materialistic-idealistic controversy as to its ultimate constitution. In his case he had repeatedly distinctly avowed his nonacceptance of metaphysical materialism, and in a few concise sentences had adduced a stronger argument against that belief than can easily be found in the literature of the subject. The same may be said about the use of the terra "vitality" by Professor Huxley and its relegation by him to the limbo of other defunct "itys." This, which has never ceased to be a red flag in the face of bellicose clergymen, was entirely within his province, and was merely a fine example of the exactness of definition of modern scientific nominalism. This misconception of the scientific use of abstraction appears in almost all the current criti-
