FOURTH LECTURE.

AUGUSTE COMTE'S PHILOSOPHY OF BIOLOGICAL SCIENCE.

PASSING from the Philosophy of Mathematics, Comte defines in what Positive Astronomy consists. He says: "Positive Religion defines Astronomy as the study of the earth as one of the heavenly bodies-that is to say, Astronomy is the knowledge of the geometrical and mechanical relations of the earth to the other stars, so far as such relations can affect our destinies by influencing the state of the earth. We subjectively, then, condense all astronomical theories round our globe as centre; and we absolutely reject all theories which, as disconnected with our globe, are by that fact at once mere idle questions, even granting them to be within our reach. This leads us finally to eliminate, not merely the so-called sidereal astronomy, but also all planetary studies which concern stars invisible to the naked eye, and which have consequently no real influence on the earth. The true domain of astronomy will now, as at the beginning of things, be limited to the five planets (Mars, Jupiter, Saturn, Mercury, Venus) which have always been known, together with the sun, equally the centre of their movements as of the earth's, and the moon, our only satellite in the heavens.

"The difference between our doctrine and that of the ancients, here, as elsewhere, consists essentially in the substitution of the relative for the absolute, so that a centre which was long objective [objective in the Ptolemaic sys

tem, and to many millions is objective even now] becomes purely subjective. Hence the discovery, or rather the proof, of the double movement of the earth is the most important of all the revolutions in science that took place while human reason was yet in its preliminary state. One of the most eminent precursors of Positivism, the sagacious Fontenelle, enabled us to see the philosophical bearing of this revolution, so far as the time admitted, in a charming little work (Les Pluralities des Mondes), which, though apparently frivolous, is justly entitled to the immortality it gained.

"In fact, the earth's motion rendered the dogmas of Positive science directly incompatible with those of any theological system. For whereas our widest speculations previously might wear the character of absoluteness, they became henceforth essentially relative. The discovery of our planetary gravitation soon followed. It was the scientific consequence of the former, and its philosophical complement....... In astronomy the point of view from which we regard the external world is simply that of Geometry and Mechanics. We put aside all inquiries, as absurd as they are idle, as to the temperature of the stars, or their internal constitution."

Of Physics, Comte goes on to say: "But when we pass from Astronomy to Physics, properly so-called, by an almost imperceptible transition through the intermediate stage of planetary mechanics, we penetrate more deeply into the study of inert nature. In order, however, to give a truer idea of this new branch of science, we must first give a conception of the highest cosmological science (Chemistry). It has a more decided character, and so enables us to grasp pure Physics, which are somewhat indefinite if you approach them directly. By adopting this course, our attention is called to one of the most important logical precepts of Positivism-that, viz., which bids us, in all cases, look first to the two extremes, if we wish to form a right conception of the intermediate step by which they are connected. Chemistry was actually introduced as a distinct science, in the East and in the West (as Alchemy), several centuries before Physics. Galileo was led by his instinct to create the science of Physics, with a view to establish a sound mode of transition from Astronomy to Chemistry, in place of the previous chimerical connection."

Comte establishes a comparison between Chemistry and Physics. He says: "At once to shorten and simplify my

explanation of the two, consider Chemistry and Physics as in the main subject to the same general influences. The difference really consists in the greater or less intensity of the modifications which the constitution of matter receives from them. But though this is the only difference, there is never any room for doubt as to the true nature of each case, spite of the confusion introduced by the schools. At their highest intensity, states of heat, of electricity, even of light, modify the contribution of matter so far as to change the internal composition of substances. In this case the event is within the department of Chemistry-that is, it comes under the general laws of composition and decomposition. In both these processes equally, we can, we ought, to look on the combination as simply binary. The combination may be repeated three times in succession. But we can seldom exceed this limit, as the union becomes more difficult and less stable in proportion as it becomes more complicated. At a lower degree of intensity the influences above mentioned can only modify the condition of bodies; they cannot alter their substance. In this case matter is studied under the strictly Physical aspect. The two sciences, Physics and Chemistry, are equally universal; but the decrease of generality is as sensible as the increase of complication, when we pass from the one to the other. For Physics, as they study the whole of the properties which make up every material existence, look on all bodies as in kind the same. The only difference is one of degree. The same branches of Physics must, then, correspond to the different senses by which we gain a knowledge of the external world. ["Physics is a group of sciences, rather than a single science, and is again divided by Comte into five departments: Barology, or the science of weight; Thermology, or that of heat; Acoustics, Optics, and Electrology. These he attempts to arrange on the same principle of increasing speciality and complexity..........All the five being essentially independent of one another, he attached little importance to their order, except that Barology ought to come first; as the connecting link with Astronomy, and Electrology last, as the transition to Chemistry." J. S. Mill.] Chemistry, on the other hand, looks on all subjects as in their nature distinct, and it chiefly addresses itself to the problem of determining their radical differences. The phenomena which it studies are always possible in any given body. But they are practically never found in it, except

under special conditions. The concurrence of these conditions is rare and difficult, so as often to demand the intervention of man."

Of the logical and scientific value of Physics and Chemistry, Comte says: "Physics are logically the most important, Chemistry scientifically. Such is our judgment on their relative encyclopædic value, when we have once allowed the indispensable necessity of both, their theoretical and practical necessity. It is in Physics that the genius of induction finds its free career, by the development of Observation, which was too spontaneous in Astronomy, and of Experiment, which nowhere else leads to such unequivocal results. But Chemistry carries the day as to the encyclopædic importance of the notions we derive from it. Its extreme imperfection, as a science, which can only cease under the discipline of Positivism, has not prevented its throwing a strong light, and exercising a powerful influence, on the whole reason of Western Europe. Its valuable efficiency in this respect is the result of its general analysis of the inorganic matter in the midst of which we livegaseous, liquid, and solid. And as the complement of this it has performed the equally indispensable analysis of the vegetable and animal substances. By this analysis we are enabled to form a conception of the fundamental economy of nature. This was previously unintelligible to us, because we had not proved that the material elements of which all real beings, lifeless as well as living, are composed, are essentially identical.

"So you may see how Chemistry, properly so-called, is alone competent to form the normal transition between Cosmology and Biology, the need of which transition you expressed by your wish for unbroken continuity. You would set a still higher value on this great encyclopædic condition, as favourable ultimately to the heart as to the intellect, were I to point out the true internal arrangement of Astronomy, Physics, and Chemistry, as I did in the case of mathematics........................... .Mathematics may serve as a type of the rest. And you may learn from it the general possibility of there being a gradual ascent from Mathematics to Morals by the simple application, with an ever-increasing exactness and detail, of the unchangeable principle of our hierarchy."

Comte concludes this part of his subject thus:-" When you come, after this Subjective or logical appreciation, to