M. Comte was accustomed to consider Descartes and Leibnitz as his princ.i.p.al precursors, and the only great philosophers (among many thinkers of high philosophic capacity) in modern times. It was to their minds that he considered his own to bear the nearest resemblance. Though we have not so lofty an opinion of any of the three as M. Comte had, we think the a.s.similation just: thes were, of all recorded thinkers, the two who bore most resemblance to M. Comte. They were like him in earnestness, like him, though scarcely equal to him, in confidence in themselves; they had the same extraordinary power of concatenation and co-ordination; they enriched human knowledge with great truths and great conceptions of method; they were, of all great scientific thinkers, the most consistent, and for that reason often the most absurd, because they shrank from no consequences, however contrary to common sense, to which their premises appeared to lead. Accordingly their names have come down to us a.s.sociated with grand thoughts, with most important discoveries, and also with some of the most extravagantly wild and ludicrously absurd conceptions and theories which ever were solemnly propounded by thoughtful men. "We think M. Comte as great as either of these philosophers, and hardly more extravagant. Were we to speak our whole mind, we should call him superior to them: though not intrinsically, yet by the exertion of equal intellectual power in a more advanced state of human preparation; but also in an age less tolerant of palpable absurdities, and to which those he has committed, if not in themselves greater, at least appear more ridiculous.
 See the Chapter on Efficient Causes in Reid's "Essays on the Active Powers," which is avowedly grounded on Newton's ideas.
 Mr Herbert Spencer, who also distinguishes between abstract and concrete sciences, employs the terms in a different sense from that explained above. He calls a science abstract when its truths are merely ideal; when, like the truths of geometry, they are not exactly true of real things--or, like the so-called law of inertia (the persistence in direction and velocity of a motion once impressed) are "involved" in experience but never actually seen in it, being always more or less completely frustrated. Chemistry and biology he includes, on the contrary, among concrete sciences, because chemical combinations and decompositions, and the physiological action of tissues, do actually take place (as our senses testify) in the manner in which the scientific propositions state them to take place. We will not discuss the logical or philological propriety of either use of the terms abstract and concrete, in which twofold point of view very few of the numerous acceptations of these words are entirely defensible: but of the two distinctions M. Comte's answers to by far the deepest and most vital difference. Mr Spencer's is open to the radical objection, that it cla.s.sifies truths not according to their subject-matter or their mutual relations, but according to an unimportant difference in the manner in which we come to know them. Of what consequence is it that the law of inertia (considered as an exact truth) is not generalized from our direct perceptions, but inferred by combining with the movements which we see, those which we should see if it were not for the disturbing causes? In either case we are equally certain that it _is_ an exact truth: for every dynamical law is perfectly fulfilled even when it seems to be counteracted. There must, we should think, be many truths in physiology (for example) which are only known by a similar indirect process; and Mr Spencer would hardly detach these from the body of the science, and call them abstract and the remainder concrete.
 Systeme de Politique Positive, ii. 36.
 The strongest case which Mr Spencer produces of a scientifically ascertained law, which, though belonging to a later science, was necessary to the scientific formation of one occupying an earlier place in M. Comte's series, is the law of the accelerating force of gravity; which M. Comte places in Physics, but without which the Newtonian theory of the celestial motions could not have been discovered, nor could even now be proved. This fact, as is judiciously remarked by M. Littre, is not valid against the plan of M. Comte's cla.s.sification, but discloses a slight error in the detail. M. Comte should not have placed the laws of terrestrial gravity under Physics. They are part of the general theory of gravitation, and belong to astronomy. Mr Spencer has. .h.i.t one of the weak points in M. Comte's scientific scale; weak however only because left unguarded. Astronomy, the second of M. Comte's abstract sciences, answers to his own definition of a concrete science. M. Comte however was only wrong in overlooking a distinction. There _is_ an abstract science of astronomy, namely, the theory of gravitation, which would equally agree with and explain the facts of a totally different solar system from the one of which our earth forms a part. The actual facts of our own system, the dimensions, distances, velocities, temperatures, physical const.i.tution, &c., of the sun, earth, and planets, are properly the subject of a concrete science, similar to natural history; but the concrete is more inseparably united to the abstract science than in any other case, since the few celestial facts really accessible to us are nearly all required for discovering and proving the law of gravitation as an universal property of bodies, and have therefore an indispensable place in the abstract science as its fundamental data.
 The only point at which the general principle of the series fails in its application, is the subdivision of Physics; and there, as the subordination of the different branches scarcely exists, their order is of little consequence. Thermology, indeed, is altogether an exception to the principle of decreasing generality, heat, as Mr Spencer truly says being as universal as gravitation. But the place of Thermology is marked out, within certain narrow limits, by the ends of the cla.s.sification, though not by its principle. The desideratum is, that every science should precede those which cannot be scientifically const.i.tute or rationally studied until it is known. It is as a means to this end, that the arrangement of the phaenomena in the order of their dependence on one another is important. Now, though heat is as universal a phaenomenon as any which external nature presents, its laws do not affect, in any manner important to us, the phaenomena of Astronomy, and operate in the other branches of Physics only as slight modifying agencies, the consideration of which may be postponed to a rather advanced stage. But the phaenomena of Chemistry and Biology depend on them often for their very existence. The ends of the cla.s.sification require therefore that Thermology should precede Chemistry and Biology, but do not demand that it should be thrown farther back. On the other hand, those same ends, in another point of view, require that it should be subsequent to Astronomy, for reasons not of doctrine but of method: Astronomy being the best school of the true art of interpreting Nature, by which Thermology profits like other sciences, but which it was ill adapted to originate.
 The philosophy of the subject is perhaps nowhere so well expressed as in the "Systeme de Politique Positive" (iii. 41). "Concu logiquement, l'ordre suivant lequel nos princ.i.p.ales theories accomplissent l'evolution fondamentale resulte necessairement de leur dependence mutuelle. Toutes les sciences peuvent, sans doute, etre ebauchees a la fois: leur usage pratique exige meme cette culture simultanee. Mais elle ne peut concerner que les inductions propres a chaque cla.s.se de speculations. Or cet essor inductif ne saurait fournir des principes suffisants qu'envers les plus simples etudes. Partout ailleurs, ils ne peuvent etre etablis qu'en subordonnant chaque genre d'inductions scientifiques a l'ensemble des deductions emanees des domaines moins compliques, et des-lors moins dependants. Ainsi nos diverses theories reposent dogmatiquement les unes sur les autres, suivant un ordre invariable, qui doit regler historiquement leur avenement decisif, les plus independantes ayant toujours d se developper plus tot."
 "Science," says Mr Spencer in his "Genesis," "while purely inductive is purely qualitative.... All quant.i.tative prevision is reached deductively; induction can achieve only qualitative prevision." Now, if we remember that the very first accurate quant.i.tative law of physical phaenomena ever established, the law of the accelerating force of gravity, was discovered and proved by Galileo partly at least by experiment; that the quant.i.tative laws on which the whole theory of the celestial motions is grounded, were generalized by Kepler from direct comparison of observations; that the quant.i.tative law of the condensation of gases by pressure, the law of Boyle and Mariotte, was arrived at by direct experiment; that the proportional quant.i.ties in which every known substance combines chemically with every other, were ascertained by innumerable experiments, from which the general law of chemical equivalents, now the ground of the most exact quant.i.tative previsions, was an inductive generalization; we must conclude that Mr Spencer has committed himself to a general proposition, which a very slight consideration of truths perfectly known to him would have shown to be unsustainable.
Again, in the very pamphlet in which Mr Spencer defends himself against the supposition of being a disciple of M. Comte ("The Cla.s.sification of the Sciences," p. 37), he speaks of "M. Comte's adherent, Mr Buckle."
Now, except in the opinion common to both, that history may be made a subject of science, the speculations of these two thinkers are not only different, but run in different channels, M. Comte applying himself princ.i.p.ally to the laws of evolution common to all mankind, Mr Buckle almost exclusively to the diversities: and it may be affirmed without presumption, that they neither saw the same truths, nor fell into the same errors, nor defended their opinions, either true or erroneous, by the same arguments. Indeed, it is one of the surprising things in the case of Mr Buckle as of Mr Spencer, that being a man of kindred genius, of the same wide range of knowledge, and devoting himself to speculations of the same kind, he profited so little by M. Comte.
These oversights prove nothing against the general accuracy of Mr Spencer's acquirements. They are mere lapses of inattention, such as thinkers who attempt speculations requiring that vast mult.i.tudes of facts should be kept in recollection at once, can scarcely hope always to avoid.
 We refer particularly to the mystical metaphysics connected with the negative sign, imaginary quant.i.ties, infinity and infinitesimals, &c, all cleared up and put on a rational footing in the highly philosophical treatises of Professor De Morgan.
 Those who wish to see this idea followed out, are referred to "A System of Logic, Ratiocinative and Inductive." It is not irrelevant to state that M. Comte, soon after the publication of that work, expressed, both in a letter (published in M. Littre's volume) and in print, his high approval of it (especially of the Inductive part) as a real contribution to the construction of the Positive Method. But we cannot discover that he was indebted to it for a single idea, or that it influenced, in the smallest particular, the course of his subsequent speculations.
 The force, however, of this last consideration has been much weakened by the progress of discovery since M. Comte left off studying chemistry; it being now probable that most if not all substances, even elementary, are susceptible of _allotropic_ forms; as in the case of oxygen and ozone, the two forms of phosphorus, &c.
 Thus; by considering prussic acid as a compound of hydrogen and cyanogen rather than of hydrogen and the elements of cyanogen (carbon and nitrogen), it is a.s.similated to a whole cla.s.s of acid compounds between hydrogen and other substances, and a reason is thus found for its agreeing in their acid properties.
 According to Sir William Hamilton, as many as six; but numerical precision in such matters is out of the question, and it is probable that different minds have the power in different degrees.
 Or, as afterwards corrected by him, the appet.i.tes and emotions, the active capacities, and the intellectual faculties; "le coeur," "le caractere," and "l'esprit."
 M. Littre, who, though a warm admirer, and accepting the position of a disciple of M. Comte, is singularly free from his errors, makes the equally ingenious and just remark, that Political Economy corresponds in social science to the theory of the nutritive functions in biology, which M. Comte, with all good physiologists, thinks it not only permissible but a great and fundamental improvement to treat, in the first place, separately, as the necessary basis of the higher branches of the science: although the nutritive functions can no more be withdrawn _in fact_ from the influence of the animal and human attributes, than the economical phaenomena of society from that of the political and moral.
 Indeed his claim to be the creator of Sociology does not extend to this branch of the science; on the contrary, he, in a subsequent work, expressly declares that the real founder of it was Aristotle, by whom the theory of the conditions of social existence was carried as far towards perfection as was possible in the absence of any theory of Progress. Without going quite this length, we think it hardly possible to appreciate too highly the merit of those early efforts, beyond which little progress had been made, until a very recent period, either in ethical or in political science.
 It is due to them both to say, that he continued to express, in letters which have been published, a high opinion of her, both morally and intellectually; and her persistent and strong concern for his interests and his fame is attested both by M. Littre and by his own correspondence.
 "Of the Cla.s.sification of the Sciences," pp. 37, 38.
 In the case of Egypt we admit that there may be cited against us the authority of Plato, in whose Politicus it is said that the king of Egypt must be a member of the priestly caste, or if by usurpation a member of any other caste acquired the sovereignty he must be initiated with the sacerdotal order. But Plato was writing of a state of things which already belonged to the past; nor have we any a.s.surance that his information on Egyptian inst.i.tutions was authentic and accurate. Had the king been necessarily or commonly a member of the priestly order, it is most improbable that the careful Herodotus, of whose comprehensive work an entire book was devoted to a minute account of Egypt and its inst.i.tutions, and who collected his information from Egyptian priests in the country itself, would have been ignorant of a part so important, and tending so much to exalt the dignity of the priesthood, who were much more likely to affirm it falsely to Plato than to withhold the knowledge of it if true from Heredotus. Not only is Herodotus silent respecting any such law or custom, but he thinks it needful to mention that in one particular instance the king (by name Sethos) was a priest, which he would scarcely have done if this had been other than an exceptional case. It is likely enough that a king of Egypt would learn the hieratic character, and would not suffer any of the mysteries of law or religion which were in the keeping of the priests to be withheld from him; and this was very probably all the foundation which existed for the a.s.sertion of the Eleatic stranger in Plato's dialogue.
 Mill, History of British India, book ii. chap. iii.
 At a somewhat later period M. Comte drew up what he termed a Positivist Calendar, in which every day was dedicated to some benefactor of humanity (generally with the addition of a similar but minor luminary, to be celebrated in the room of his princ.i.p.al each biss.e.xtile year). In this no kind of human eminence, really useful, is omitted, except that which is merely negative and destructive. On this principle (which is avowed) the French _philosophes_ as such are excluded, those only among them being admitted who, like Voltaire and Diderot, had claims to admission on other grounds: and the Protestant religious reformers are left out entirely, with the curious exception of George Fox--who is included, we presume, in consideration of his Peace principles.
 He goes still further and deeper in a subsequent work. "L'art ramene doucement a la realite les contemplations trop abstraites du theoricien, tandis qu'il pousse n.o.blement le praticien aux speculations desinteressees." Systeme de Politique Positive, i. 287.
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 Systeme de Politique Positive, iv. 100.
 See Sir John Herschel's Outlines of Astronomy, -- 319.
 Synthese Subjective, pp. 10, 11.
 Synthese Subjective, pp. 11, 12.