any

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the same with the second law of motion,-Galileo's law of the reconciliation of any common motion with various particular motions,-which is extensible to all phenomena, inorganic and organic, all active and passive mutual relations being radically independent of any action which is precisely common to the parts concerned. In biology, we find this true in the cases of sensibility and contractility; for, our impressions being purely comparative, our appreciation of partial differences is not interfered with by any general and uniform influence. In sociology, we find it again; disturbance in the interior of any political system being due to the unequal progressive action on the different parts which, if participating in the movement in any equal degree, would be unaffected by a much more rapid progression. We discern an analogous case in the physico-chemical province, in thermometrical effects referrible to mutual inequality, and we shall no doubt encounter many more when the science is further developed. As to the third law of • motion,-Newton's law of the equivalence of action and reaction,-its universality is more striking than in the other two cases; and it is the only case of the three in which the principle has hitherto been perceived and proposed. If we adapt our observation to the spirit of the corresponding phenomena, there is no doubt that the equivalence of action and reaction may be as really observed with regard to physical, chemical, biological, and social effects as in the case of mechanical effects. Besides the mutual quality inherent in all actions, it is certain that the general estimate of mechanical reaction, in the combination of masses and velocities, everywhere meets with an analogous appreciation. If Berthollet has shown the chemical influence of mass, before misconceived, an equivalent discussion would manifest no less clearly its biological or political influence. The close and prevalent interconnection which distinguishes vital, and yet more social phenomena, and in which all aspects are mutually dependent, is eminently fit to familiarize us with the universality of this third law of motion. Each of the three laws on which rational Mechanics is founded is, in fact, only a mechanical manifestation of a general law, applicable to all possible phenomena. In order to illustrate this most important approximation, it must be

extended, further, to the famous general principle by which D'Alembert completely connected questions of motion with questions of equilibrium. Whether it is regarded, as I propose, as a happy generalization of the third law of motion, or is still regarded as a distinct idea, it is in conformity with a universal conception by which the dynamical is always connected with the statical appreciation, the laws of harmony being always maintained in the midst of the laws of succession. Sociology here again affords us the most decisive exemplification (though often only implicit) of this general relation because the two aspects are more marked and more interconnected than in any other case. .If we could thoroughly know the laws of existence, I have no doubt that we should find them all, as in mechanics, to .be mere questions of action. But, though we must proceed in an inverse manner, we proceed upon the same conception of the necessary convergence between the statical and the dynamical conclusions. It is only that the universal principle is employed in a new mode, in conformity with the nature of the phenomena; of which sociological speculation has often presented important examples. The laws of rational mechanics are then only the earliest philosophical manifestation of certain general laws, necessarily applicable to the natural economy of any kind of phenomena whatever. Though they must first be recognized in regard to the simplest and most general case of all, it does not follow that they are due to the mathematical spirit, which at present is the chief obstacle in the way of their being understood. The conception results from the first scientific reaction of the positive spirit proper to organic studies, and sociological speculation particularly, on fundamental ideas which have hitherto seemed proper to inorganic researches. Its philosophical value lies in its establishing an identity between the primary laws of the two extreme orders of natural phenomena and the delineation I have now offered is intended to point out here, in the only case compatible with the extreme imperfection of science, the first type of the new character of universality which must belong to the chief positive ideas under the natural ascendancy of the true philosophical spirit. We have no equivalent case at our command: and in more complex subjects, these general

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laws can only go a part of the way in directing our speculations; though they will always afford valuable scientific guidance and suggestion, because they must always govern more special laws, relating to other abstract modes of existence and activity. Whether, as we may hope, these more special laws may in time obtain universality among their respective phenomena or not, we are now authorized in conceving the whole system of our knowledge as susceptible, in certain respects, of a true scientific unity, independently of the logical unity, though in complete agreement with it. If Mathematics furnishes us with the laws The Astronoof inorganic existence, Astronomy discloses mical element. to us the medium, which is no less universal.. Our examination of it may appear a departure from the great Baconian precept about the abstract nature of the speculations proper to the first philosophy: astronomical ideas being in fact nothing else than mathematical notions restricted to the case of the stars. But, true as this is, there is another view, the same as that which justified the incorporation of the analysis of air and water with abstract chemistry; that our study is not concrete, inasmuch as it relates to the general medium, which is truly abstract and unchangeable. The mathematical phenomena of astronomy remain abstract, as if the bodies they relate to could admit of no other; whereas the character of a concrete theory consists in the direct and permanent combination of the different modes inherent in each total existence. astronomy, mathematical speculations do not lose their abstract nature, and only exhibit it in a case so important that we are compelled to make it special; its difficulties also constituting the chief destination of mathematical research, as well as its best logical instigation. The reaction on mathematics, again, affords us the most striking evidence of the reality and the scope of its conceptions. Here, again, the human mind obtains its first systematic sense of a necessary economy, arising from invariable relations proper to corresponding phenomena, and affording, by its inaccessible sway, a rule of conduct. This is the source of the philosophical guidance of collective Man which is carried out by training in the case of individual Man. Yet, the human point of view must prevail in this case, to secure

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the rationality of the corresponding studies; because our radical ignorance of cosmical laws, and our restriction to our own system, prevent our obtaining any external view of astronomical science. We find in astronomy the first instance of the encroachments of the mathematical spirit in an empirical way; but, as we have seen, the fault affects only the logical administration, and does not produce the scientific dangers which it occasions in the more complex departments, because it is in full conformity with the nature of astronomical research.

The Physical. In Physics, a new action is first recognized, more compound and essentially modifying the simpler. All physical phenomena are common to all bodies; but their manifestation requires a concurrence of circumstances, more or less compound, and not continuous. Of the five physical categories, Weight alone presents a really mathematical generality, thus being the natural transition between astronomy and physics. The others exhibit an increasing speciality, by which I have classed them. The importance of this province, in connection with that of chemistry, will appear if we try to imagine that such a transition from the mathematical to the organic sciences did not exist for we shall see how all conception of unity must disappear if science consisted of two elements so heterogeneous, which could admit of no permanent relation; even supposing that the positive spirit could arise at all. This intermediate element is so connected with the others at each extremity as to constitute a sufficiently perfect scale. Some difficulties however arise out of this position, which will always largely affect the inherent imperfections of the duplicate science, the subject of which presents neither the simplicity of the first couple nor the characteristic interconnection of the last. We have seen how little prospect there is of scientific unity among the heterogeneous parts of which physics is composed; and the greater probability is that the number of irreducible elements will hereafter be increased; for the diversity must correspond not only with the subjects studied, but with our organic means of investigation. Of the five existing subjects, two address themselves to one sense each,-one to hearing and another to sight; and these can never be made to coincide. The other

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three relate equally to sight and touch: and yet no one will venture to regard thermology and electrology as susceptible of fusion with barology, or with each other, however indisputable are certain relations between them. Moreover, the actual number of our external senses is by no means finally ascertained, so immature is at present the whole theory of sensation. A truly rational inquiry would, no doubt, show that we have two senses relating to temperature and pressure, which are both now confounded with that of touch, which seems to include all the offices whose special seat is not clearly determined. It is evident, again, that smell and taste, largely needed in chemistry, have no function in physics; yet it seems that each of them must have ere this constituted a department for itself, like sight and hearing, if our organization had been in this respect as perfect as that of many of the higher animals. The mode of inorganic existence which is disclosed by smell, seems in fact to be not less distinct from those which correspond to the other senses than they are from each other; of which the persistence and power of the sense through the whole animal series is an evidence. Our organic imperfection may perhaps be to a certain degree compensated by an artificial investigation, which may afford some scientific extension; and an improvement of our relations with the higher animals may conduce to the same end. Meantime, it is clear that the number of irreducible elements that constitute Physics, is not yet even rationally fixed. Till it can be, the science remains peculiarly liable to the encroachments of mathematical and metaphysical abuse. The imperfections of its nature and method of culture, however, cast no doubt upon its rank in the scale of sciences. That rank is settled by the universal principle of decreasing generality; and the principle obviates the worst inconveniences of the multiple character of physics by instituting a gradual transition from the barological speculations which unite it to astronomy, and the electrological which border upon chemistry.

As for Chemistry, considered separately, it The Chemical. relates to so intimate and complete a mode

of inorganic existence, that it has been found difficult to separate it from the organic. The phenomena of various