Hans Jonas, Philosophical Essays, “Seventeenth Century and After: The Meaning of the Scientific and Technological Revolution”
III
How this came about is a story involving many things besides the history of science. The movement that remade thought from its foundations was not an isolated event but had a background commensurate in breadth with its own dimension in depth. We cannot go here into the manifold aspects of the crisis that attended the transition from medieval to modern man. Among them are the rise of the cities which eroded the feudal order, the concurrent rise of national monarchies, the expansion of trade, the spreading of information through the printing press, the maritime voyages of discovery which widened the physical and mental horizons. . . . Widening the horizons, and in rather abrupt manner, was the general signature of the age. From the relatively closed compass of Christian Europe, Western man moved into the expanding world of modern enterprise and global politics. External and internal barriers were breaking down everywhere. New outlooks, often confused, were born, and paid their toll of infant mortality. With the broadened ethnological knowledge of humankind in the variety of its beliefs and customs — matched in the historical dimension by the new knowledge of the Classics — came a new skepticism concerning the validity or inevitability of one’s own inherited ways (vide Montaigne). Every province of human affairs came to be affected by these changes, and at the center the conception which man held of himself and his relation to the universe. The discovery of the autonomous individual — of his worldly glory in the Italian Renaissance, of his religious conscience in the Northern Reformation — elevated personal insight and judgment to unprecedented authority. In exchange, almost everything else became insecure. To try out new ways became natural.
In the midst of this ferment of many liberations and gropings, appeared the book that ushered in the scientific revolution: Copernicus On the Revolutions of the Celestial Orbs. It is not amiss to remember that the same year, 1543, saw the publication of Vesalius’ On the Fabric of the Human Body. The fact is symbolic of the two sides of the scientific revolution as it eventually took shape: the macrocosmic and the micro-cosmic, the abstract and the concrete, the mathematical and the empirical, construction and observation — the unifying conception of the total scheme of things and the differentiating perception of particular detail. But it is not surprising that of these two sides it was the first which proved to be the effectively revolutionary factor in the revolution: revolutions always are what they are by their abstract component. Let us now look at the main traits of this metamorphosis of speculative thought.
Taking as known the direct content of Copernicus’ feat in astronomy — the replacement of the geocentric by a heliocentric system through the hypothesis of a double, axial and orbital, movement of the earth, with the resultant simplification of theory compared to the cumbersome Ptolemaic scheme — we fix our attention on certain implications of the new theory which were not at all in its inventor’s mind, but which inevitably led to a new physical cosmology far beyond any merely mathematical reinterpretation of astronomical data. Let us consider these three: (1) the necessarily implied proposition of the homogeneity of nature throughout the universe; (2) the absence of a solid architecture of the universe to account for its orderliness; and (3) its probable infinity, by which it ceased to be a “whole” or a “cosmos” in the sense of a determinate entity.
1. The entirely novel conception that nature is the same everywhere, be it heaven or earth, followed from the non-geocentric cosmology by the simple fact that the earth had become a “star” itself, viz. a planet, and by the same token the planets had become “earths.” Instead of enjoying a nobler, more refined and sublime type of being, they were instances of the same physical reality as the one we are familiar with on this gross, material, heavy earth. Thus, with one stroke, the essential difference between the terrestrial and celestial spheres, between sublunar and stellar, corruptible and incorruptible nature vanished: and with this, the idea of any natural order of rank lost its most telling support in the visible scheme of things. If not even the universe in its majesty is a hierarchical order, if the heavens themselves are assimilated to earth, then nature as such may not be a hierarchical principle at all and not bestow privileges of sublimity anywhere. The newly interpreted evidence of the universe pointed to its being homogeneous throughout.
This homegeneity means, to begin with, that the universe is everywhere composed of the same kind of matter — the same substance: this would in due course lead to the more far reaching postulate that it is also everywhere subject to the same laws. The first notion alone had to overcome deep-seated habits of thought, sanctioned by the tremendous authority of Aristotelian teaching. It was the main burden of Galileo’s telescopic observations of the heavenly objects to lend visual proof to the argument of substantial sameness and confute the Aristotelians on this point (and by implication on the larger issues of cosmology). If there are mountains and valleys on the moon and spots on the sun; if the planets are seen as disks (showing that they are spherical bodies of differing magnitudes) and Venus as subject to phases (showing that it shines with reflected light) — then the eye can see what reason must infer from the Copernican theory: that the astronomical objects are material bodies in space of no “purer” substance than other bodily things. To us, who have long been accustomed to thinking of “heavenly” bodies in no other way and have actually seen men walking on the moon, it is not easy to appreciate the spectacular impact which this first ocular display of physical detail had not only on the direct issue, viz., the material nature of the stars, but on the verification of the total world-hypothesis from which it was but one marginal inference — and one hardly contemplated by Copernicus himself. In the case of the sun spots, incidentally, observation here exceeded the inference from theory, which directly extended only to the nature of the planets, as companions of the earth: the sun, in the original “heliocentric” scheme, occupied a qualitatively unique position as the ruling center (which to Kepler assumed almost mystical significance) and was therefore exempt from the physical generalization otherwise invited by the theory in its initial form. Equally so was the sphere of the fixed stars, the outermost circumference of the world cavity, which had been removed to extremes of distance from the solar family at its core, so that all of its former bonds to our world were cut (as discussed below). But this very disconnection, as we shall see, instead of offering a refuge to qualitative diversity, eventually resulted in the inclusion of sun and stars in the unifying argument.
Anticipating this result, we may add already the functional complement to the “substantial” aspect of homogeneity. If made of the same substance throughout, as suggested by the substantial sameness of earth and planets, the universe can reasonably be expected to obey the same laws in all its parts. This would mean that the same physics applies to the heavens that is found to operate on earth. There was, of course, little point in stressing this inference before there was a physics to make good the promise it held out. But once the laws of motion were discovered, through the combination of abstract reasoning and terrestrial experiment which Galileo’s genius initiated, their extrapolation to the celestial world — to everything in the world — followed naturally from the implied homogeneity of the “Copernican” universe. With the triumphal success of this extrapolation in Newton’s feat, the “mathematical” construction of Copernicus and Kepler was at last vindicated as a physical cosmology. The identical laws holding throughout the universe turned out to be the laws of mechanics.
2. Let us consider now the second of the three implications of the Copernican revolution we have set out to explicate: the dissolving of the solid cosmic architecture which had guaranteed the orderly working of the Aristotelian-Ptolemaic universe. Laws of motion indeed became a necessary desideratum to explain the orbits of the planets when those moving celestial objects were no longer thought to be attached to revolving orbs. The discarding of such “orbs” or “spheres” followed from a theoretical development somewhat more complicated than the one we have just discussed. First we must recall the function of these time-honored constructs of earlier cosmology.
The concept of heavenly spheres is closely connected with the axiom that all cosmic motion is circular. This idea, originally impressed on the imagination by the visible revolution of the star-studded night sky around the celestial pole, had gained the quality of a metaphysical principle and become wedded to ideas of perfection which were associated with the geometrical properties of the circle. Such excellence alone was thought fitting for the most perfect part of corporeal nature. The two a priori requirements, therefore, which every cosmic motion — as distinct from sublunary motions — had to satisfy were circularity of path and uniformity of speed. But only the diurnal motion of the total sky, i.e., the collective revolution of the fixed stars, fulfilled this double requirement directly and visibly. It alone also presented the immediate appearance of a great hollow sphere revolving about an invisible axis drawn through the poles. The irregular motions of the planets, with their “stations” and “retrogradations,” were only indirectly, by an ingenious multiple combination of eccentrics and epicycles, brought into consonance with the general axiom. Complicated as the resulting system was, it generally succeeded in saving the phenomena with fair accuracy. But beyond this calculatory aspect, the system had this important physical aspect that it required force merely to account for the fact of motion and not for its shape: the latter followed simply from the shape of movable structures, endowed with just one “degree of freedom.” Whatever rides on the circumference of a wheel or axially rotating sphere cannot but describe a circular path. Thus, given .1 certain spatial order of cycles, and cycles mounted on cycles (etc.), conceived like rigid bodies; and given one continuous impulse, imparted lo the outer sphere by the First Mover and hence transmitted down the system through the concentric spheres, nothing more is required to produce the path of any particular star in all its complexity. Since it was not the moving force, but the form of the structures moved, that defined the form of particular movement, one efficient cause sufficed to eternally supply the motion as such: the rest followed from the coeternal matrix of differentiating structures on which it acted. Thus no dynamics of interacting forces was called for, merely a geometry of constraining forms. In other words, the “physics” of the heavens is not a kinetics, but an architectonics with one basic form — circularity — “natural” to the heavens as such and reserved to them alone.
This solid architecture of the cosmos dissolved in the wake of Copernicus’ reinterpretation of celestial mathematics. Copernicus himself, still clinging to the axiom of circularity, could not yet dispense with a system of cycles and epicycles (though greatly diminished in number) to account for the astronomical facts. But the opaque, earth-like, no longer ethereal bodies into which the planets had changed, were ill fitted for the continued association with transparent spheres that were to carry them around. And the fixed stars, since their motion had become merely apparent, no longer stood in need of a vehicle at all; so at least the outer sphere, the original model of all the postulated spheres, had lost its raison d’être — which was that of all spheres, viz., to be the vehicle of stellar movement. The immobilized Great Sphere was thus the first to become theoretically redundant: it so happened that in historical fact — since it did not contradict theory — it was the last to go. With it went the venerable idea of the vaulted heaven — another of the many victims which Copernican doctrine extracted from the appearances of sense.
The death blow was dealt to the concept of spheres as such by Kepler’s discovery of the elliptic orbits. It was a threefold deathblow: to the axiom of circularity, to the axiom of uniformity, and to the total conception of a structured world space. The first follows from Kepler’s first law of planetary motion (the law of the ellipse) and requires no explanation. The second follows from the second law (the law of areas), stating the variation of orbital velocities between the maxima at perihelion and the minima at aphelion. The third follows from both together; no combination of uniformly revolving, rigid structures would yield for any point this combination of elliptic path with the required asymmetric variation of speed. Whatever was to be done about the outer sphere — and Kepler himself, from a dislike of infinity, still held to it — for the planets it was obvious that they were attached to nothing. The inescapable conclusion was that they were independent bodies, moving freely through empty, featureless space. And the inescapable question arose: What, then, holds them in their orbits and determines their varying velocities?
Already Kepler himself felt the weight of this novel question arising from his discoveries, and groped for an answer. The law of areas clearly pointed to a force directed toward the sun and dependent on distance from it. From there on, the quest for causes of motion, that is, for a dynamics that would explain the empirically discovered, purely descriptive laws — that would furnish their common why, and in direct application would yield the particular movement of each planet as a causal necessity — became the order of the day. It had to wait for Newton to reach its goal.
3. A third unpremeditated consequence from Copernican doctrine — with a far more than physical significance — was the extension of the world to infinity. It was set in motion almost immediately after the appearance of the new theory, in response to one of the earliest objections raised against it. The failure of any trace of a parallax to be detected in the fixed stars, which should be there as counterpart to the alleged annual revolution of the earth, either refuted the notion of a moving earth altogether, as the anti-Copernicans contended, or it put those stars at such a distance as to make the effect of the earth’s motion unobservable: which was the rejoinder of the Copernicans. This sounds like a mere technical, upward revision of cosmic magnitudes. But this is a case where quantity turns into quality. Given the enormous length of the diameter of the orbis magnus (the earth’s orbit around the sun), the observational zero value of any triangulation from this truly cosmic base to the outer sphere called for an almost unimaginable lengthening of the radius of that sphere — to a magnitude which no longer bore any relation to former beliefs about the size of the universe. According to those former beliefs, the cosmos — closed, though of quite imposing dimensions — presented a well-proportioned distribution of entities occupying the space between the earth and the outer limit. Now, with the leap in dimensions, this outer limit, becoming implausible itself as an entity in its monstrous magnification, presided over the immense emptiness of a cavity in whose center huddled the solar system. And since this great sphere, the locus of the fixed stars, had already lost its other and more convincing role, that of diurnal revolution, little was needed for the final step to deny its bounding role as well — that is, to discard it altogether, and to pass from the closed to the open universe. Thus, what started as an embarrassment to theory (the missing parallax) led by its immanent logic to a profound change of world view. It must be said that the first, momentous steps toward infinity were taken under duress and without exuberance.
Exuberance, however, was soon to seize upon the half-finished thought and sweep it to its bold conclusions. Where the astronomers moved warily, the impatience of the visionary forged ahead and with one stroke translated all the latent potentials of the Copernican hypothesis into a majestic, new, intoxicating vista of the infinite universe. It is in essentials still ours. I speak of Giordano Bruno, who proclaimed the infinity of the world not as a concession to be made to the exigencies of theory, but as an inspiring and liberating revelation which alone was in keeping with the inner nature of things. [I refer the reader to Alexander Koyre’s beautiful book, From the Closed World to the Infinite Universe (Baltimore: The Johns Hopkins Press, 1957).] This only martyr of the scientific revolution, himself not a scientist, became the prophet of “the decentralized, infinite and infinitely populous universe” (Lovejoy). Stated briefly, Bruno realized, and drew together, the following implications of the new astronomy, one or the other of which had singly found some lower-keyed statement before.
a. When looking at the night sky, we do not look at a confining vault but into the depth of infinite space.
b. The luminaries seen there are not at an equal radius — however large — from the earth, but are scattered ad infinitum through this depth.
c. Even the nearest of them is so distant (vide the argument of the parallax), that its mere visibility and apparent size [To the naked eye (and still to the earliest telescopes) the fixed stars have some angular dimension.] requires us to assign it a real size comparable to that of the sun.
d. The stars are indeed suns and — since their space is the same as ours and conditions are alike everywhere — must be thought as attended by planets as well, too small in size and luminescence to be seen from our distance.
e. The universe therefore consists of worlds upon worlds in infinite multitude, and abounds with life and immanent creativity.
f. The universe has no center: its infinity is the coequal company of all the infinitely numerous bodies which it contains. Each of these is the center of its own surrounding space, but none has a privileged position with respect to the whole. (Bruno thus abolished the short-lived cosmic centrality which the sun had just gained through Copernicus in replacing that of the earth, and which the great Kepler still upheld a generation later in express opposition to Bruno’s rush into infinity.)
g. The world space itself is a homogeneous void, though pervaded by invisible forces (conceived by Bruno in rather magical terms), through which there is universal communication among the dispersed worlds, and their multiplicity fuses into unity. (Bruno thus did not wait for Kepler’s laws to do away with any remnant of a structural architectonics of world space: in principle, his vision had left only a dynamics — still to be specified — to provide the ordering necessity for the scattered pluralism in the unstructured void.)
h. The infinity of the universe, far from contradicting the nature of creation (which was of necessity finite to medieval-theological thought, as infinity befits God alone), is on the contrary the necessary and only adequate expression of the infinity and perfection of the creative cause, which totally expresses itself in its product, is constantly at work within it — is indeed not distinct from it.
This enumeration of objective doctrine conveys nothing of the hymnic tone, the almost inebriated mood, with which Bruno propounded it through the length and breadth of a Europe girding itself for the longest religious war in its history. This burning spirit greeted the opening of the universe like the crumbling of prison walls, as an outer infinity congenial to the infinity in man. It is only fair to add that in the following century, with a chillier air, a very different voice was heard in response to the — by then no longer controversial — infinity of the physical universe. “Cast into the infinite immensity of spaces of which I am ignorant, and which know me not, I am frightened” — thus Pascal expressed the contrary mood it may elicit, the mood of cosmic solitude. Bruno; lonely among men, welcomed cosmic infinitude as the revelation of a divine superabundance of reality and something kindred to himself; Pascal shrank from it and felt the loneliness of mankind in an alien universe. But whatever the response, the cosmos and man’s place in it had changed beyond recognition.