ism of Büchner, who derives all the phenomena of life from simple combinations of matter and force; second, the atheism of Comte, whose scientific pretensions Mr. Huxley ridicules, and whose results Mr. Spencer impugns; third, the identification of mind and motion by Mr. Taine, which Tyndall, in one of his most eloquent passages, says explains nothing, and is, moreover, utterly "unthinkable;" and, fourthly, Mr. Spencer's evolutionism, which, in spite of the marvellous ingenuity and information with which it is wrought out, seems to me, after no little study, as it does to others more capable than I am of forming a judgment, after greater study, to be full of un-supported assumptions, logical inconsistencies, and explanations that explain nothing, while in its general character it tends to the sheerest naturalism. Now, was I right or wrong in regarding these systems as speculative merely, and not scientific? Am I to infer, from your objections to my remarks, that The Popular Science Monthly holds materialism, atheism, and naturalism to be the legitimate outcome of science? Else why am I arraigned for designating them as unworthy of science, and as having no rightful claims to the name, under which their deplorable conclusions are commended to the public?
My object in these allusions was to indicate two capital distinctions, which it is always important to keep in view when estimating the scientific validity of a doctrine. The first is, that many questions determinable by science are not yet determined by it; and, until they are so determined, are to be regarded only as conjectural opinions, more or less pertinent or impertinent. Of this sort I hold the Nebular, the Darwinian, and the Spencerian views to be, i. e., hypotheses entirely within the domain of scientific theory, and capable, to a certain extent, of explaining the phenomena to which they refer; highly plausible and probable even at the first glance; but disputed by good authority, and not at all so verified as to be admissible into the rank of accredited science. They are suppositions to which the mind resorts to help it in the reduction of certain appearances of Nature to a general law; and, as such, they may be simple, ingenious, and even beautiful; but thus far they are no more than suppositions not proved, and therefore not entitled to the authority of scientific truth. You are probably too familiar with the history of scientific effort—which, like the history of many other kinds of intellectual effort, is a history of human error—not to know that, while hypothesis is an indispensable part of good method, it is also the part most liable to error. The records of astronomical, of geological, of physical, of chemical, and of biological research, are strewn with the débris of abandoned systems, all of which once had their vogue, but none of which now survive and many of which are hardly remembered. Recall for a moment the Ptolemaic cycles and epicycles; recall Kepler's nineteen different hypotheses, invented and discarded, before he found the true orbital motion of Mars; recall in geology Werner and Hutton, and the Plutonians and the Neptunians, superseded by the uniformitarians and the catastrophists, and now giving place to the evolutionists; recall in physics the many imponderable fluids, including Lamark's resonant fluid, that were held to be as real as the rocks only a few years ago; recall in chemistry, not to mention the alchemists and phlogistion, a dozen different modes of accounting for molecular action; recall in biology the animists and the vitalists, the devotees of plastic forces, of archei, of organizing ideas, and of central monads, all of them now deemed purely gratuitous assumptions that explained nothing, though put forth as science.
Even in regard to the question, so much discussed at present, of the gradual progression and harmony of being, the old monadology of Leibnitz, which endowed the ultimate units with varying doses of passion, consciousness, and spontaneity, and which built up the more complex structures and functions of organisms, from the combination of these—this theory, I say, somewhat modified and stripped of its mere metaphysical phases, could be made quite as rational and satisfactory as the more modern doctrines of development. Indeed, some eminent French philosophs—Renouvier, a first-class thinker, among the rest—have gone back to this notion; Darwin's suggestion of pangenesis, and Mr. Spencer'a physiological units, look toward it; and
