I.—The Atomic Materialism.

The material hypothesis, as I read it, and as alone I propose to comment on it, maintains that, with ultimate inorganic atoms to begin with, the present universe could be constructed. Before it can be tested, its datum (inorganic atoms) must be pressed into more determinate form by an explanation of the word "atoms." "Things which cannot be cut" might be all alike; or they might be variously different inter se: and before we start, we must know on which of these two assumptions we are to proceed. The former is the only admissible one, so long as you credit the materialist with any logical exactness. When he asks for no more than matter for his purpose, he must surely be understood to require nothing but the essentials of matter, the characters which enter into its definition; and to pledge himself to deduce out of these all the page 22 accessory characters which appear here and not there, and which discriminate the several provinces of nature. The idea of atoms is indeed simply the idea of "matter" in minimis, arising only from an arrest, by a supposed physical limit, of a geometrical divisibility possible without end; and the attributes which suffice to earn the one name give the meaning of the other. When in mathematical optics the investigator undertakes, from the conditions afforded by an undulatory elastic medium, to deduce the phenomena of refraction and polarization, he is not permitted to enlarge the data as he proceeds, and surreptitiously import into his ether chemical or other characters unnamed at first. Just as little can one who proposes to show the way from simple atoms to the finished world be allowed to swell the definition of those atoms at his convenience, and take on fresh attributes which change them from matter, , and make them now this sort of matter, now that. Whatever he thus adds to his assumption is filched from his quæsita, to the relief of his problem and the vitiation of its proof: and if the whole fulness of the quæsita is so withdrawn, and turned back to be condensed into datum, all deduction is given up, and the thesis is simply taken for granted.

In precisely this plight,—unless there is some reasoning between the lines which I am too dull to see,—Professor Tyndall leaves his case. He ridicules me for defining the assumed atoms as "homogeneous extended solids," on the ground that a phrase thus restricted to the "requisites of body" gives only "a metaphysical body."^* Everything

^* It becomes still more metaphysical in the hands of an eminent teacher of physical science. "L'impénétrabilité," says Pouillet, "c'est la matifère. On n'a pas raison de dire que la matière a deux propriétés essentielles, Pétendue et Pimpénérabilité; ce ne sont pas des propriétés, c'est une définition." And again, "L'impénétrabilité inséparable est ce qu'on appelle un atome."—Eléments de Physique expérimentale, Tom. i. p. 4.

page 23 which you define is, in the same sense, a "metaphysical" (more properly, a "logical") subject. The object of the definition is to specify the attributes which alone are to be considered in giving the name, and in reasoning from it. The atomist who is not content with my account of his premisses should oblige me with a better, instead of stopping short with the discovery that a definition of a class is not a full description of its individuals. When, however, I look about for my critic's correcter version of "matter" or its atoms, it is long before I learn more than that "we must radically change our notions" of it,—an injunction upon which, without further help, it is difficult to act. At length, however, on the concluding page of the critique, the missing definition turns up. "Matter I define as that mysterious thing by which all this has been accomplished," i.e. the whole series of phenomena, from the evaporation of water to self-conscious life of man. Need I say that such a proposition is no definition, and dispenses with all proof; being simply an oracle, tautologically declaring the very position in dispute, that matter carries in it "the promise and potency of all terrestrial life"? The whole of the picturesque group of descriptive illustrations which lead up to this innocent dictum are only an expansion of the same petitio principii: they simply say, over and over again, the force immanent in matter is matter;—they are identical; or if not so as hitherto understood, we will have a new definition to make them so. This is not a process of reasoning, but an act of will,—a decretal enveloped in a scientific nimbus. Nothing can be less relevant than to show (and nothing else is attempted) that the forces of heat, of attraction, of life, of page 24 consciousness, are attached to material media and organisms, which they move and weave and animate: this is questioned by no one. In the sense of being immanent in matter, and manifesting themselves by its movements, they are material forces; but not in the sense of being derivable from the essential properties of matter, quâ matter. And this is the only sense on which philosophies divide, and reasoning is possible.

If the essence of the materialist hypothesis be to start with matter on its lowest terms, and thence work up into its highest, I did it no wrong in taking "homogeneous extended solids" as its specified, datum, and its only one; so that it constituted a system of "monism." Dr. Tyndall asks me "where and by whom" any such datum is "specified." In the Contemporary Review, June, 1872, Mr. Herbert Spencer contends that "the properties of the different elements" (i.e. chemical elements, hydrogen, carbon, &c.) "result from differences of arrangement, arising by the compounding and recompounding of ultimate homogeneous units." Here, totidem verbis, is the monism which I am charged with "putting into the scheme." As my critic is evidently anxious to disclaim the monistic datum, I conclude that he owns the necessity of heterogeneous elements to begin with, and feels with me the insecurity of Mr. Spencer's deduction of chemical phenomena from mechanical. Though I have the misfortune, in the use of this same argument,—that you cannot pass from the homogeneous to the heterogeneous,—to incur the disapproval of two great authorities, it somewhat relieves the blow to find Mr. Spencer at one with the premiss, and Dr. Tyndall ratifying the conclusion.

Before I quit this point I ought perhaps to explain, in deference to Mr. Spencer, why I venture to repeat an argu- page 25 ment which he has answered with care and skill. In common with all logical atomists, he appeals to the case of isomeric bodies, and especially to the allotropic varieties of carbon and phosphorus, to prove that, without any change of elements in kind or proportion, and even without any composition at all, substances present themselves with marked differences of physical and chemical property. There are several distinct compounds formed out of the same relative weights of carbon and hydrogen. And the simple carbon itself appears as charcoal, as black-lead and as diamond; and phosphorus, again, in the yellow, semi-transparent, inflammable form, and as an opaque, dark-red substance, combustible only at a much higher temperature. In the absence of any variation in the material, these differences in the product are attributed to a different grouping of the atoms; and whatever their form, it is easy, within certain limits, to vary in imagination the adjustments of their homologous sides, so as to build molecules of several types, and ultimately aggregates of contrasted qualities.

I admit that, on the assumption of homogeneity, we may provide a series of unlike arrangements to count off against a corresponding number of qualitative peculiarities, though it is doubtful whether the conceivable permutations can be pushed up through the throng of cases presented by organic chemistry. But the morphological differences, if adequately obtained, contribute no explanation of the observed variations of attribute. "What is there in the arrangement a b c to occasion "activity" in phosphorus, while the arrangement b a c produces "inertness"? Where the products differ only in geometrical properties, and consequently in optical, the explanation may be admissible, the form and the laying of the bricks determining the outline and the page 26 density of the structure. But the deduction cannot be extended from the physical to the chemical properties, so as to displace the rule that to these heterogeneity is essential. To treat the cases of allotropy as destructive of a rule so broadly based, and fly off to a conjectural substitute, is surely a rash logic. In these cases certainly we know of no difference of composition. But neither do we know of any difference of arrangement. The first, if we could suppose it latently there, would be a vera causa of the unexplained phenomena; the second, though its presence were ascertained, would still rank only as a possible cause of them. If, therefore, an inquirer chose to say, "From this difference of property I suspect a difference of composition," what answer could we give him from Mr. Spencer's point of view? Could we say, "We finally know carbon to be simple"? On the contrary, we are warned that "there are no recognized elementary substances, if the expression means substances known to be elementary. What chemists for convenience call elementary substances are merely substances which they have thus far failed to decompose." If we are to stand ready to see sixty-two out of the sixty-three "elements" fall analytically to pieces before our eyes, how can we feel so confident of the simplicity of phosphorus or carbon, as to make it answerable for a hypothetical reconstruction of chemical laws?

Even in the last resort, if we succeed in getting all our atoms alike, we do not rid ourselves of an unexplained heterogeneity; it is simply transferred from their nature as units to their rules of combination. Whether the qualitative difference between hydrogen and each of the other elements is conditional upon a distinction of kind in the atoms, or on definite varieties in their mode of numerical or geometrical union, these conditions are not provided page 27 for by the mere existence of homogeneous atoms; and nothing that you can do with these atoms, within the limits of their definition, will get the required heterogeneity out of them. Make them up into molecules by what grouping or architecture you will; still the difference between hydrogen and iron is not that between one and three, or any other number; or between shaped solids built off in one direction and similar ones built off' in another, which may turn out like a right and a left glove. If hydrogen were the sole "primordial," and were transmutable, by select shuffling of its atoms, into every one of its present sixty-two associates, both the tendency to these special combinations, and the effects of them, would be as little deducible from the homogeneous datum as, on the received view, are the chemical phenomena from mechanical conditions. I still think, therefore, that if you assume atoms at all, you may as well take the whole sixty-three sorts in a lot. And this startling multiplication of the original monistic assumption I understand Professor Tyndall to admit as indispensable.

Next, in the striking words of Du Bois-Reymond, I had pleaded the impossibility of bridging the chasm between Chemistry and Consciousness. The sensations of warmth, of sound, of colour, are facts sui generis, quite other than the undulations of any medium, the molecular movements of any structure; known on different evidence, compared by different marks, needing a different language, affections of a different subject; and defying prediction and interpretation, on the part of a stranger to them, out of any formulas of physical equilibrium and motion, or of chemical affinity and composition. They, with all the higher mental conditions, belong to a world beyond the bounds of the natural sciences,—a world into which they can never find page 28 their way, its phenomena being intrinsically inappreciable by their instruments of research. Here, then, in this establishment of two spheres of cognition, separated by an impassable gulf, we surely have a breach in the continuity of our knowledge: on the one side, all the phenomena of matter and motion; on the other, those of living consciousness and thought. Step by step, the "Naturforscher" may press his advance, through even the contiguous organic provinces; but at this line his movement is arrested; he stands in presence of that which his methods cannot touch;—an intellectual necessity stops him, and that for ever, at the boundary which he has reached. With this doctrine I invited my readers to compare the statement of Professor Tyndall, that, relying on "the continuity of nature," he "cannot stop abruptly where microscopes cease to be of use," but "by an intellectual necessity crosses the boundary," and "discerns in matter the promise and potency of all terrestrial life," including, therefore, conscious life. This statement appeared to me inconsistent with Du Bois-Reymond's "limit to natural science," and still appears so. What is my critic's reply? He cites another statement of his own, which is quite consistent with the doctrine of the eminent Berlin Professor and anticipates it; a procedure by which he answers himself, not me;—and, instead of removing the contradiction, takes it home. If, as the earlier passage says, "the chasm between the two classes of phenomena" (physical processes and facts of consciousness) "remains intellectually impassable," the "intellectual necessity of crossing the boundary" is not easy to understand. In order to "discern in matter the promise" of conscious life, you must be able, by scrutiny of its mere physical movements, to forecast, in a world as yet insentient, the future phenomena of feeling and thought. Yet this is precisely the transition page 29 which is pronounced "unthinkable;" "we do not possess the intellectual organ, nor apparently any rudiment of the organ, which would enable us to pass, by a process of reasoning, from the one to the other." If between these statements "nothing but harmony reigns," then indeed I am justly charged with being "inaccurate."

How then does the case stand with the atomic hypothesis, as a starting-point of scientific deduction? In Dr. Tyndall's latest exposition we have it admitted—(1) that the monistic doctrine of homogeneous units will not work, and that the assumption must be enlarged to include heterogeneous chemical atoms; (2) that nothing which we can do with this magnified datum will prevent our being finally stopped at the boundary of consciousness. As these two positions are precisely those which I had taken up against the speculative materialist, it is an infinite relief to discover, when the mask of controversy is removed, the features of a powerful ally. The whole argument sums itself up in Sir William Thomson's remark, "The assumption of atoms can explain no property of body which has not previously been attributed to the atoms themselves."

That the totality of sensible and deducible phenomena is produced by a constant amount of forces in a given quantity of matter, is a legitimate principle of modern science, and an adequate key for the interpretation of every proved or probable evolution. And in order to see what is comprised in changes that are intricately woven or fall broadly on the eye, it is often needful to take them to pieces and microscopically scrutinize them. We thus discover more exactly what they are, and how at the moment they are made up; and by doing likewise with the prior and posterior conditions of the same group, we learn to read truly the metamorphoses of the materials before us. But this is page 30 all. To suppose that by pulverizing the world into its least particles, and contemplating its components where they are next to nothing, we shall hit upon something ultimate beyond which there is no problem, is the strangest of illusions. There is no magic in the superlatively little to draw from the universe its last secret. Size is but relative, magnified or dwindled by a glass, variable with the organ of perception: to one being, the speck which only the microscope can show us may be a universe; to another, the solar system but a molecule; and in passing from the latter to the former you reach no end of search or beginning of things. If in imagination you simply recede from the molar to the molecular form of body, you carry with you, by hypothesis, all the properties of the whole into the parts where your regress ceases, and merely substitute a miniature of nature for its life-size, without at all showing whence the features come. If, on the other hand, you drop attributes from the mass in your retreat to the elements, on your return you can never pick them up again: starve your atom down to a hard, geometrically perfect minimum, and you have parted with the possibility of feeding it up to the qualitative plenitude of our actual material forms; for in mere resistance,—which is all that is left,—you have no source of new properties, only the power of excluding other competitors for its place.

Accordingly, the "atom" of the modern mathematical physics has given up its pretension to stand as an absolute beginning, and serves only as a necessary rest for exhausted analysis, before setting forth on the return journey of deduction. "A simple elementary atom," says Professor Balfour Stewart, "is probably in a state of ceaseless activity and change of form, but it is, nevertheless, always the same."^*

^* The Conservation of Energy, p. 7.

page 31 "The molecule" (here identical with "atom," since the author is speaking of a simple substance, as hydrogen) "though indestructible, is not a hard rigid body," says Professor Clerk Maxwell, "but is capable of internal movements, and when these are excited it emits rays, the wave-length of which is a measure of the time of vibration of the molecule."^* "Change of form" and "internal movements" are impossible without shifting parts and altered relations; and where, then, is the final simplicity of the atom? It is no longer a pure unit, but a numerical whole. And as part can separate from part, not only in thought but in the phenomenon, how is it an "atom" at all? What is there, beyond an arbitrary dictum, to prevent a part which changes its relation to its fellows from changing its relation to the whole,—removing to the outside? Such a body, though serving as an element in chemistry, is mechanically compound, and has a constitution of its own, which raises as many questions as it answers, and wholly unfits it for offering to the human mind a point of ultimate rest. It has accordingly been strictly kept to a penultimate position in the conception of philosophical physicists like Gassendi, Herschel, and Clerk Maxwell, and of masters in the logic of science, like Lotze and Stanley Jevons.

It is a serious question whether, in our time, atomism can any longer fulfil the condition which all the ancient materialism was invented to satisfy. The Ionian cosmogonies sprang from a genuine intellectual impulse; the desire to conquer the bewildering multiplicity of nature, and find some pervading identity which should make a woven texture of the whole; and whether it was moisture, or air, or the ether-fire, which was taken as the universal substratum, it was regarded as a single datum, on the

^* A Discourse on Molecules, p. 12.

page 32 simplicity of which the mind might disburden itself of an oppressive infinitude. The intention of these schemes was to unify all bodies in their material, and in some cases all minds as well, so as not even to allow two originals at the fountain-head, but to evolve the All out of the One. This aim was but an overstraining of the permanent effort of all scientific interpretation of the world. It strives to make things conceivable by simplification, to put what was separate into relation, what was confused into order; to read back the many and the different into the one and the same, and so lessen, as far as possible, the list of unattached and underived principia. The charm of science to the imagination and its gain to life may be almost measured by the number of scattered facts which its analysis can bring into a common formula. The very sand-grains and rain-drops seem to lose in multitude, when the morphological agencies are understood which crystallize and mould them. The greatness of Newton's law lies in the countless host of movements which it swept from all visible space into one sentence and one thought. No sooner does Darwin supply a verified conception which construes the endless differences of organic kinds into a continuous process, than the very relief which he gives to the mind serves, with others if not with himself, as an equivalent to so much evidence. The acoustic reduction of sounds, in their immense variety, to the length, the breadth, and the form of a wave, is welcomed as a happy discovery from a similar love of relational unity. To simplify is the essence of all scientific explanation. If it does not gain this end, it fails to explain. Its speculative ideal is still, as of old, to reach some monistic principle whence all may flow; and in this interest it is, especially to get rid of dualism by dissolving any partnership with mind, that materialism continues to page 33 recommend its claims. Does it really bring in our day the simplification at which it aims?

Under the eye of modern science, Matter, pursued into its last haunts, no longer presents itself as one undivided stuff, which can be treated as a continuous substratum absorbent of all number and distinction; but as an infinitude of discrete atoms, each of which might be though all the rest were gone. The conception of them, when pushed to its hypothetical extreme, brings them no nearer to unity than homogeneity,—an attribute which itself implies that they are separate and comparable members of a genus. And what is the result of comparing them? They "are conformed," we are assured, "to a constant type with a precision which is not to be found in the sensible properties of the bodies which they constitute. In the first place, the mass of each individual," "and all its other properties, are absolutely unalterable. In the second place, the properties of all" "of the same kind are absolutely identical."^* Here, therefore, we have an infinite assemblage of phenomena of Resemblance. But further, these atoms, besides the internal vibration of each, are agitated by movements carrying them in all directions, now along free paths and now into collisions,^† Here, therefore, we have phenomena of Difference in endless variety. And so it comes to this, that our unitary datum breaks up into a genus of innumerable contents, and its individuals are affected both with ideally perfect correspondences and with numerous contrasts of movement. What intellect can pause and compose itself to rest in this vast and restless crowd of

^* Discourse on Molecules, by J. Clerk Maxwell, M.A., F.R.S., p. 11.

^† Theory of Heat, by J. Clerk Maxwell, M.A., LL.D., F.R.SS. London and Edin., pp. 310, 311.

page 34 assumptions? Who can restrain the ulterior question,—whence then these myriad types of the same letter, imprinted on the earth, the sun, the stars, as if the very mould used here had been lent to Sirius and passed on through the constellations? Everywhere else the likenesses of individual things, especially within the same "species,"—of daisy to daisy, of bee to bee,—have awakened wonder and stimulated thought to plant them in some uniting relation to a cause beyond themselves; and not till the common parentage refers them to the same matrix of nature does the questioning about them subside. They quietly settle as derivative where they could never be accepted as original. Some chemists think, as Mr. Herbert Spencer reminds us,^* that in the hydrogen atom we have the ultimate simple unit. By means of the spectroscope, samples of it, and of its internal vibrations, may be brought from Sirius and Aldebaran—distances so great that light itself needs twenty-two years to cross the lesser of them—into exact comparison with our terrestrial specimens; and were their places changed, there would be nothing to betray the secret. So long as no à priori necessity is shown for their quantity of matter being just what it is, and always the same at incommunicating distances, or for their elasticity and time of pulsation having the same measure through myriads of instances, they remain unlinked and separate starting-points; and if they explain a finite number of resemblances and differences, it is only by assuming an infinite.

But even the approach to simplicity which homogeneity would afford fails us. Notwithstanding the possibility, in the case of certain carbonates, of substituting isomorphous constituents for one another, it cannot be pretended that

^* Contemporary Review, June, 1872, p. 142.

page 35 any evidence as yet breaks down the list of chemical elements: and, should some of them give way before farther attempts at analysis, they are more likely—if we may judge of the future from the past—to grow to a hundred than to dwindle to one: to say nothing of the probability, already suggested by the star-spectroscope, that in other regions of space there exist elements unknown to us. At present, in place of a single type of atom, we have to set out with more than sixty, all independent, and each repeating the phenomenon of exact resemblance among its members wherever found. Perhaps you see nothing inconceivable in the self-existence of ever so many perfect facsimiles ready everywhere for the making of the worlds, and may treat it as a thing to be expected that, being there at all, they should be all alike. So much the more certain, then, must be your surprise on finding them not all alike, but ranging themselves under sixty heads of difference. If the similars are entitled to the position of , the dissimilars are not: and if neither can prefer the claim, the atomic doctrine, when pushed into an ultimate theory of origination, extravagantly violates the first condition of a philosophical hypothesis.

Nor is its series of assumed data even yet complete. For these sixty kinds of atoms are not at liberty to be neutral to one another, or to run an indeterminate round of experiments in association, within the limits of possible permutation. Each is already provided with its select list of admissible companions; and the terms of its partnership with every one of these are strictly prescribed; so that not one can modify, by the most trivial fraction, the capital it has to bring. Vainly, for instance, does the hydrogen atom, with its low figure and light weight, make overtures to the more considerable oxygen element: the only reply will be, page 36 Either none of you or two of you. And so on throughout the list. Among the vast group of facts represented by this sample, I am not aware of more than one set—the union of the same combining elements in multiple doses for the production of a scale of compounds—of which the atomist hypothesis can be said to render an account. Everything else,—the existence of "affinity" at all, its limitation to particular cases so far short of the whole, the original cast of its definite ratios, its preference for unlike elements,—stands unexplained by it, or must be carried into it as a new burden of primordial assumptions. This chasm between the facts of chemistry and its speculations is clearly seen by its best teachers. Kekulé treats the symbolic notation of chemical formulas as a means of simply expressing the fact of numerical proportion in the combining weights.

"If to the symbols in these formulas" (he adds) "a different meaning is assigned, if they are regarded as denoting the atoms of the elements with their weights, as is now most common, the question arises, 'What is the relative size or weight of the atoms?' Since the atoms can be neither measured nor weighed, it is plain that to the hypothetical assumption of determinate atomic weights we have nothing to guide us but speculative reflection."^*

The more closely we follow the atomist doctrine to its starting-point, and spread before us the necessary outfit for its journey of deduction, the larger do its demands appear; and when, included in them, we find an unlimited supply of absolutely like objects, all repeating the same internal movements,—an arbitrary number of unlike types, in each of which this demand is reproduced, and a definite selec-

^* Lehrbuch der organischen Chemie, ap. Lange, Geschichte des Materialising, ii. p. 191.

page 37 tion of rules for restricting the play of combination among these elements,—we can no longer, in the face of this stock of self-existent originals, allow the pretence of simplicity to be anything but an illusion.

Large as the atomist's assumptions are, they do not go one jot beyond the requirements of his case. He has to deduce an orderly and determinate universe, such as we find around us, and to exclude chaotic systems where no equilibrium is established. In order to do this he must pick out the special conditions for producing this particular kosmos and no other, and must provide against the turning up of any out of a host of equally possible worlds. In other words, he must, in spite of his contempt for final causes, himself proceed upon a preconceived world-plan, and guide his own intellect as, step by step, he fits it to the universe, by the very process which he declares to be absent from the universe itself. If all atoms were round and smooth, he thinks no such stable order of things as we observe could ever arise; so he rejects these forms in favour of others. By a series of such rejections he gathers around him at last the select assortment of conditions which will work out right. The selection is made, however, not on grounds of à priori necessity, but with an eye to the required result. Intrinsically the possibilities are all equal (for instance), of round and smooth atoms, and of other forms; and a problem therefore yet remains behind, short of which human reason will never be content to rest, viz.: How come they to be so limited as to fence off competing possibilities, and secure the actual result? Is it an eternal limitation, having its "ratio sufficiens" in the uncaused essence of things; or superinduced by some power which can import conditions into the unconditioned, and mark out a determinate channel for the "stream of ten- page 38 dency" through the open wilds over which else it spreads and hesitates? It was doubtless in view of this problem, and in the absence of any theoretic means of excluding other atoms than those which we have, that Herschel declared them to have the characteristics of "manufactured articles." This verdict amuses Dr. Tyndall; nothing more. He twice^* dismisses it with a supercilious laugh; for which perhaps, as for the atoms it concerns, there may be some suppressed "ratio sufficiens." But the problem thus pleasantly touched is not one of those which solventur risu; and, till some better-grounded answer can be given to it, that on which the large and balanced thought of Hersehel and the masterly penetration of Clerk Maxwell have alike settled with content, may claim at least a provisional respect.

Having confined myself in this section to the Atomic Materialism, I reserve for the next the consideration of the Dynamic Materialism, and the bearings of both on the primary religious beliefs. To those—doubtless the majority in our time—who have made up their minds that behind the jurisdiction of the natural sciences no rational questions can arise, and from their court no appeal be made, who will never listen to metaphysics except in disproof of their own possibility, I cannot hope to say any useful word: for the very matters on which I speak lie either on the borders of their sphere, or in quite another. I am profoundly conscious how strong is the set of the Zeit-geist against me, and should utterly fail before it, did it not sweep by me as a mere pulsation of the Ewigkeits-geist that never sweeps by. Nor is it always, even now, that physics shut up the mind of their most ardent and successful votary within their own province, rich and vast

^* Belfast Address, p. 26. Fortnightly Review, Nov. 1875, p. 598.

page 39 as that province is. "It has been asserted," says Professor Clerk Maxwell, "that metaphysical speculation is a thing of the past, and that physical science has extirpated it. The discussion of the categories of existence, however, does not appear to be in danger of coming to an end in our time; and the exercise of speculation continues as fascinating to every fresh mind as it was in the days of Thales."^*