Nicolas Copernicus’s reform of astronomy delivered a formidable blow to our sense of self in nature. In its effects, Copernicanism probably affected human consciousness more deeply than Darwinism. Published in 1543, On the Revolutions of the Heavenly Spheres argued that our earthly globe is not the unique and motionless centre of the great cosmic sphere. Only a hundred years later educated Europe believed that the Sun is the central linkage around which the Earth and the other planets revolve, and that observed changes in the positions of the Sun, the Moon and the distant stars result from the Earth’s motion alone, and not from the motion of a huge starry sphere whirling around a fixed Earth. This reform shattered once and for all a comforting and enduring picture of our place in the cosmic scheme of things. In this scheme, first proposed by Aristotle in the fourth century BC, everything has a place in an ordered hierarchy. The heavenly spheres are immutably nested one within the other, and each carries one of the heavenly bodies (e.g. Sun, Moon and planets) in circular motion around the fixed Earth placed at the geometrical centre of the cosmic sphere. In the terrestrial region (the region below the Moon’s sphere) air and fire, if not prevented, move naturally upwards towards their natural places: in contrast, the elements of earth and water move directly downwards. According to Copernicus, however, the Earth hurtles through space, wheeling around its axis as, in company with the other planets, it encircles the Sun. This meant that the planets, the wandering stars, were now downgraded to the level of the mundane Earth; or, put differently, the Earth itself was now a wandering star. Either way, the distinction was broached between the perfection of the heavens and the imperfection of the terrestrial realm. In consequence, some perennial questions were raised anew: what is man’s place in the scheme of things? Does nature exist for the sake of man? Is there any intelligible order to be found in the cosmic scheme? And how is the Earth’s motion to be reconciled with Scripture, experience and tradition?
It is this dramatic shift that Hans Blumenberg seeks to explain. To this end he sets himself the task of tracing the origin, significance and consequences of Copernicus’s treatise. For Blumenberg the impact of Copernicus cannot be reduced to an episode in the history of astronomy. It is, rather, the beginning of a changing focus in human awareness, which starts to forge a new sense of destiny in a cosmos seemingly devoid of coherence.
Blumenberg poses two central questions. Why was a reception for Copernicus’s treatise possible historically in 1543, when the same Sun-centred astronomical reform (advocated by Aristarchus of Samos) had been decisively rejected in the third century BC? And how did the implications in Copernicus’s treatise for our view of God, the cosmos and man become acceptable culturally during the 16th and 17th centuries? In short, how did a view of the cosmos that was previously unimaginable, and certainly intolerable to received opinion, become a plausible candidate for human acceptance? In pursuing these questions, Blumenberg is not concerned simply to explain how an innovative idea actually comes about. His concern lies rather in mapping out the ‘latitude’ of possible changes consistent with a culture’s prerogatives and thereby with the possibilities that it excludes. In other words, for Blumenberg an account of an audience’s reception of an idea tells more about its viability than a prehistory of its genesis. This approach demands a firm grasp of a culture’s inner dynamic, of its global perspectives and of its deepest motivations.
It is in the cultural context of the Aristotelian cosmos of hierarchic spheres that Blumenberg depicts the drama of Copernicus’s innovation and the possibility of its occuring when it did. Copernicus’s impact was decisive and immediate. He argued that the Earth is more than just a moving body, it is in fact the primary body which moves in the cosmic scheme. Not only did this view break decisively with the principles of order and hierarchy intrinsic to traditional astronomy, it also obliterated the distinction between the immutable perfection of the rotating heavenly spheres, and the mundane fixity of the habitable Earth. More dramatic still, Copernicus showed that the rotation of the great stellar sphere, far from being the primary physical reality, was but a mere appearance explained by the axial rotation of the Earth itself. With this step he also reversed the origin and direction of cosmic change, which now no longer originated with the stellar sphere to flow inward from the outside to the centre, from above to below, but arose from the Earth’s motion at the very interior of the stellar sphere itself. Thus, at one stroke, Copernicus annulled tradition by reducing the eternal mobility of the heavens to the status of a mere appearance caused by the real rotation of the lowest of all physical bodies, the Earth. He also argued that apparent complexities in the observed motions of the other planets arise from their speeds relative to the Earth’s speed, as they and the Earth form a system of bodies moving around the Sun. What was for traditional astronomy planetary ‘appearances’ explained by complex models, became for Copernicus a direct consequence of the relative speeds of the Earth and the other planets. Thus Copernicus stopped the heavens, and made apparent what had formally been taken to be a fact.
If the authority of Aristotle’s cosmology was still paramount in Copemicus’s time, however, and if Copemicus’s astronomy relies on devices used by earlier astronomers, such as Ptolemy, how is the acceptance of Copernicus to be explained historically and culturally? Blumenberg argues that the cosmological authority of Aristotle had in fact been weakened over the centuries. But how is this to be explained? Ptolemy himself had argued that Aristarchus’s Sun-centred astronomy is to be rejected primarily because it violates the explanatory principles of Aristotle’s cosmology. In this opinion he was followed by most astronomers. To explain the weakening of Aristotle’s authority, and the possibilities for change which that allowed, Blumenberg advances two main accounts.
He reminds that the geocentric and heliocentric models of the planetary system were known to be equivalent from the time of Plato. Thus the technical side of Copernicus’s reform caused no consternation. It was quite another matter, however, if the heliocentric model were taken to reflect the actual structure of the planetary system, as Copernicus believed. To counteract objections to this perspective the possibility of contemplating worlds other than Aristotle’s was, in Blumenberg’s view, paramount. This theoretical ‘licence’ began with the 1277 Paris Condemnation of Aristotelianism. Among other things, the Condemnation emphasised the fear that the Aristotelian conception of what is possible in the order of nature would constrain the power and freedom of the Christian God. It therefore stated that nature need not be arranged according to the principles of Aristotle’s cosmology. Indeed, God could have chosen to actualise possible worlds other than the world he did in fact actualise. This opinion did not impugn Aristotle’s authority as a whole: on the contrary, Aristotle’s views provided the only comprehensive system of cosmology until the early Renaissance. But it did permit thinkers to articulate counterfactual alternatives to Aristotle justified by the claim that God could have done otherwise. For example, in the 14th century, Bradwardine and Oresme imagine God moving the entire cosmos from one ‘place’ into another ‘place’ in imaginary space. This view allows the possibility, contrary to Aristotle, that space may be infinitely extended and that our cosmos may be only one world among many situated in such a space.
Oddly enough, in his account of the impact of the Condemnation, Blumenberg does not discuss Bradwardine’s views, nor does he discuss the alternative worlds envisioned by Oresme. Yet both thinkers cast doubt on the Aristotelian claim that the cosmos is a unique and finite sphere beyond which nothing can exist. Moreover, they seriously entertain the notion that time is the consequence of God’s enduring omnipresence, and not merely the measure of Aristotle’s rotating cosmos. Interestingly enough, Blumenberg himself devotes much effort to discussing changing views on the origin of time, and to explaining how the reality of time gets detached from the rotation of Aristotle’s cosmic sphere. Indeed, he must. One of the dramatic consequences of Copernicus’s reforms is that Aristotle’s rotating cosmos is now stopped; nevertheless, the origin and uniformity of time still need to be accounted for.
Other 14th-century thinkers entertained more daring possibilities. Buridan, for example, extends an important theory of how things move against their nature (e.g. how a stone continues to move upwards when propelled) to the natural motion of all bodies, including the heavenly bodies. This is the theory of impetus which says that the stone continues to move because an impetus or motive force is implanted in it by the thrower. According to Buridan, it is God who imparted a downward inclination in earth and an opposite inclination in fire. Moreover, at the time of creation God also implanted an impetus in the Sun, Moon and other heavenly bodies. This view marks a decisive break with Aristotle’s physics. It tends to minimise the distinction between natural and non-natural motion, and explains the natural motions of the heavens by the same principles as the mundane motions of the sublunary bodies. But precisely this break with Aristotle had already occurred in the sixth century AD in the writings of the Christian Neoplatonist Philoponus. Blumenberg is silent on Philoponus’s influence in the Middle Ages, and on his impact in the Renaissance when his views were widely disseminated in Latin translation. The 16th century knew that Philoponus denied the divinity of the heavens by arguing that the physical universe began simultaneously with God’s creation. They were familiar, too, with his denial of the eternal rotation of the heavens and his claim that they are made of earthly fire, not a fifth element which rotates naturally. Equally well-known was Philoponus’s development of the theory of impetus, and his use of it to explain the motions of all created bodies, including the heavens. In short, they knew that a systematic and original attack had been made on Aristotle, and had been assimilated into both Islamic and Western culture.
The impact of the 1277 Condemnation on scientific culture in the West has been much discussed. Blumenberg is hardly on new ground here. It is strange, then, that he fails to provide any discussion of the doctrine of God’s absolute and ordinary power, given that the implications of this doctrine are what the Condemnation is all about. In virtue of his absolute power God could have actualised any one of a series of possible worlds other than the one he created, and by whose laws he now abides by his ordinary power. This distinction in God’s power is an ancient one which can be traced back to the Christian apologist Origen, who drew it to answer pagan objections to Christianity. If, as Aristotle argued, things are determined by their natures, is the Christian God able to change nature? If he cannot, his power is abrogated: if he can, the notion of a settled order is bankrupt. Origen’s answer is to contrast what God could have done with what he has done and to add that God abides with the natural order because he created it and it is good. The distinction in God’s power is relevant to Blumenberg’s discussion, yet he makes the barest reference to it, and fails to indicate its significance as a pre-condition for Copernican reform.
The distinction is relevant to another important topic which Blumenberg does discuss. This is the conception of ‘accompanying causality’ and ‘communicated causality’. A fundamental expression of ‘accompanying causality’ is the Aristotelian principle that every change or motion demands an agent which simultaneously causes that change or motion. In the Christian context, in which an all-powerful God is both the first and the sustaining cause of all that is and comes to be, it would seem that God must be everywhere in his creation to sustain and change it. How then does Christianity avoid Pantheism as a logical outcome of its causal principles? Again, by invoking the distinction between God’s absolute and ordinary power. God realises his absolute power in the world that he creates by ‘communicating’ efficacy to that world. Without God, of course, the created world would fail to continue in its existence, so God must ‘accompany’ the world in order to sustain it. It is a pity that Blumenberg does not discuss these connections, since they are germane to his analysis.
The second part of Blumenberg’s analysis of what made Copernicanism possible is of more interest. He tells a compelling story of changing relations between anthropocentrism, geocentrism and theocentrism. He argues that there is no mutual entailment between anthropocentrism and geocentrism. Blumenberg challenges the belief that deep historical connections obtain between an anthropocentric view of human nature and the geocentric cosmology of Aristotle. Indeed, for Aristotle, anthropology is subordinate to cosmology, even though his cosmos is geocentric. Only the ancient Stoics held that God and man are citizens of one cosmic polis, with God, man and the cosmos engaged in a drama of mutual fulfilment. Blumenberg also reminds us how different these views are from the one which predominates in Christianity. In Christian thought the cosmos is alien to man’s redemptive destiny. Moreover, it must yield to the Biblical injunction of dominion over nature and ultimately to the cosmos’s destruction in the conflagration that will at last ensure human salvation. Thus, in Christianity there is an ever-present tension between the cosmology of a created world and the redemptive needs of man. This view is clearly theocentric. Little wonder, then, that Blumenberg sees no dominant tradition of anthropocentric interpretations of geocentrism. If man’s removal from the centre of the world caused a trauma, it was not because Copernicus prised apart anthropocentrism and geocentrism by putting the Earth into motion. Indeed, for Copernicus we are at the centre of the world, not because of our place in the hierarchy of being, or because of the privilege of a geocentric position, but because we are able to understand the world as an object of our reflective thought. In fact, Copernicus’s humanist anthropocentrism, with its denial of geocentrism as a condition of the dignity of man, was a view widely shared in the 16th century.
Of great interest is Blumenberg’s account of how Galileo and Kepler advocated the truth of Copernicanism. He is right to insist that Copernicus’s astronomical reform required a fundamental rethinking of the physics of the world. Right, too, in insisting that Copernicus’s essentialism – the view that physical bodies rotate and revolve circularly because they are spherical was inadequate to underwrite the physical truth of heliocentrism. Galileo, it is true, adhered to the view that spheres rotate naturally, ignored Kepler’s laws of regulated motion along elliptical paths, and perhaps placed too much weight on the telescope as a means of revealing the truth of the Earth’s annual motion. He did show, however, that if the Earth were moving uniformly we should expect the character of our experience to be no different from what it would be if it were at rest. After all, the stone falls to the bottom of the ship’s mast in the same manner whether the ship is at rest or in uniform motion. Why, then, expect objects to be left behind as the Earth progresses along its path? Galileo also combined horizontal motion together with accelerated downwards motion (according to his law of uniform acceleration) to account for the parabolic motion of projectiles. These were important contributions to the new physics. Blumenberg neglects, however, to take their measure in his over-concern to censure Galileo for being too much the telescopic observer.
Blumenberg’s treatment of Kepler as a Copernican is exemplary. It was Kepler who broke with the circularity of planetary motion and with the ‘physics’ of the sphere in favour of ellipses. Moreover, he argued that the Sun is the physical centre of the planetary system and the force which drives the planets. Causality was now truly directed from the centre, with its effects on the planets precisely expressed in mathematical laws relating their speeds and positions along elliptical paths. For Blumenberg, that is the true foundation of Copernicanism: a programme of dynamic astronomy based on physical causes which emanate from a Sun-centred world, a programme brought brilliantly to completion with the publication of Newton’s Principia in 1687.