Leviathan and the Air-Pump: Hobbes, Boyle and the Experimental Life 
by Steven Shapin and Simon Schaffer.
Princeton, 475 pp., £40, February 1986, 0 691 08393 2
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‘Scientists’ in our culture are (in many disciplines) people who perform ‘experiments’ in ‘laboratories’ and ‘testify’ about them to a wider community of like-minded people who then try to draw conclusions from the ‘facts’ put before them. The subject of this entertaining and important study is in effect the emergence of this practice and the removal of quotation-marks from these hitherto contentious or puzzling terms. Steven Shapin and Simon Schaffer are historians of ‘science’ who were led by their discontent with the hegemony of experimentation to study the controversy between Robert Boyle, patron saint or founding shaman of the experimental method, and his most profound and systematic opponent Thomas Hobbes: a controversy which began in 1661 with the publication of Hobbes’s Dialogus physicus de natura aeris and which continued in a variety of forms into the 1670s. Leviathan and the Air-Pump is the result of that study, and it includes as an appendix an almost complete translation (by Schaffer) of the Dialogus physicus.

The air-pump in the book’s title was Boyle’s proudest example of experimentation. It was a glass globe which could be evacuated of air by means of a piston, and into which experimental apparatus (such as the Torricellian column of mercury, or barometer) could be inserted. On one occasion a live pigeon was placed in the globe and the assembled philosophers watched it suffocate. As Shapin and Schaffer stress, air-pumps were ‘big science’, being expensive objects which were difficult to make and were thinly distributed among the European philosophical community. It is no accident that Boyle’s father had been the richest man in the British Isles before the Irish Rebellion of 1641, and the family was still immensely wealthy after the Restoration. With a characteristically sardonic touch, Hobbes alluded to the ‘mechanical’ character of Boyle’s experimental labours: ‘not every one that brings from beyond seas a new gin, or other jaunty device, is therefore a philosopher. For if you reckon that way, not only apothecaries and gardeners, but many other sorts of workmen, will put in for, and get the prize.’ (Boyle’s supporter John Wallis retaliated by openly sneering at Hobbes’s plebeian-sounding surname.)

Shapin and Schaffer were quickly led to realise that much wider issues were at stake in the controversy than merely the status of experiment. ‘Testifying’ about experiments to a community of ‘scientists’ raises the question of who constitutes that community and what witnessing experiments consists in. As they point out, the very term ‘laboratory’ originally had overtones of hermeticist secrecy, whereas it was a key feature of Boyle’s experimental programme that his laboratory and those of his friends in the early Royal Society should be open to a public. But they were not open to the public, a point Hobbes made much of: access to the experiments was still controlled by their ‘master’, as Hobbes described him. Questions of political control were thus directly raised by the use of experiments to authorise scientific theories: for experiments were the preserve of a self-appointed group of professionals whose claim to authority was no better than those of the other groups which Hobbes devoted his life to attacking – notably the clergy of an established church.

At a deeper level, however, Shapin and Schaffer also believe that the whole issue of what constituted justified belief and what the ‘facts’ were was at stake, and that this too had obvious political implications – it was his distinctive position on these matters which Hobbes apparently used as the foundation for his political theory, from the Elements of Law in 1640 to Leviathan in 1651, and beyond. I am less persuaded by this claim of theirs than by their other remarks about the problem of authority.

Although Shapin and Schaffer do not discuss this in any detail, it is clear that the general background to the debate between Hobbes and Boyle was the sceptical culture of the late 16th and early 17th centuries. Both traditional, Aristotelian science, and the new sciences of Italian seers such as Telesio or Bruno, had been attacked by sceptical writers like the late 16th-century Frenchmen, Montaigne and Pierre Charron. They mounted two separate arguments, one against the physical sciences and the other against the moral sciences. Against the former, they insisted that plain observations of the world (of the kind fundamental to Aristotelian realist physics) were impossible. Human perception was prone to error, and a variety of familiar optical illusions were adduced to make this point. Against the latter, they argued that the multiplicity and radical incompatibility of human moral beliefs and practices could not be overcome, and that there was no common criterion which agents from all societies would accept as a touchstone for their ethical beliefs.

Trying to answer these two arguments in a persuasive, non-Aristotelian way became a major enterprise, particularly in France, in the second and third decades of the 17th century. Descartes of course participated fully in the enterprise, but so did Hobbes (both men revolving round the figure of Marin Mersenne – another philosophical ‘master’, according to Hobbes). Hobbes’s physical and moral theories were clearly designed to overcome the sceptic whilst conceding the force of his examples: thus Hobbes always stressed both the impossibility of direct acquaintance with anything outside one’s own thought-processes or ‘fantasies’, and the absence of any objective common criterion for moral belief. ‘Every man, for his own part,’ he said in Elements of Law, ‘calleth that which pleaseth, and is delightful to himself, GOOD.’ He freely used the repertory of examples of optical illusion and moral conflict which the sceptics employed: indeed, there are many passages in Hobbes which read exactly like Charron.

Hobbes’s answer to the sceptic about physics was merely that there was an a priori correct structure of reasoning about the natural world. One and only one notion of cause made sense: this was the idea that a moving material object impinges upon another material object and causes it to move also. Notions of, for example, immaterial objects or self-moving ones were all logically flawed in some straightforward way. We have direct acquaintance with our ‘fantasies’: they exhibit the property of change, and the changes must be caused by some process which is describable in these a priori terms. This is as far as Hobbes went in his physics, and he consistently argued that any account of the physical processes leading to a particular ‘fantasy’ was purely hypothetical.

His answer to the sceptic about ethics was of an appropriately different kind. Here, he argued that all men will concede that prima facie another man has the right to defend himself. ‘It is not against reason that a man doth all he can to preserve his own body and limbs, both from death and pain. And that which is not against reason, men call RIGHT, or jus, or blameless liberty of using our own natural power and ability’ (Elements). This is a ‘common’ description of the liberty, according to Hobbes: there is no reason why we cannot all ascribe this right to our fellow-men, even as we try to destroy them in order to protect ourselves. Given Hobbes’s concept of a right, we can concede that they have the same rights against us as we have against them. The problem of the state of nature is then that it is not clear what in any particular instance actually conduces to our preservation, or who is ‘really’ a threat to us: we all differ on that, and it is our differences about this ‘matter of fact’ which causes the notorious bellum omnium contra omnes.

Hobbes’s solution was in line with his general epistemic strategy. He avoided saying that there was a ‘real’ truth of the matter that we ought to agree on, but instead argued that in these situations of uncertainty about the implementation of our right, we should ‘artificially’ eliminate the uncertainty by handing over our power of judgment to a common sovereign. We could not do so where there was no uncertainty: thus if someone was directly and obviously attacking us, we could still defend ourselves. But in the absence of such an uncontentious threat, the sovereign decided for us what was dangerous and what was not. His judgment would be no more accurate than ours – there could not be an accurate account of the natural world. But it would correspondingly be no less accurate, and so we would be no worse off with him making the decisions for us. (A historical note: if this account of Hobbes’s theory is right, then it is fairly obvious what the original issue was which led him to think about politics. The question of whether the sovereign was the only person entitled to make judgments about his people’s protection was the central issue in the Ship Money case of 1637.)

I have stressed the anti-sceptical roots of Hobbes’s philosophy because Shapin and Schaffer on the whole do not, and this leads them to the most intellectually difficult sections of their book. The problem is that Boyle advertised his own ‘scepticism’ repeatedly: his most famous work is a dialogue called The Sceptical Chymist (1661), and the principal interlocutor in it is named Carneades – the major philosopher of Academic scepticism in antiquity, familiar to all Early Modern intellectuals from the pages of Cicero. Boyle’s argument about the provisional or hypothetical character of any physical explanation was the same as Hobbes’s, and though (like the historical Carneades, and unlike Hobbes) he was willing to talk about more or less ‘probable’ opinions, it is not on the face of it clear that his sceptical approach conflicted with that of Hobbes.

Nor, most strikingly, is it clear that it conflicted with that of Hobbes’s main philosophical associate, Pierre Gassendi. Gassendi was another participant in the epistemological enterprise orchestrated by Mersenne: like the others, he began as a sympathiser with modern scepticism, and he never wholly repudiated it. His view was that while the deception of the senses can never be wholly overcome, the use of scientific instruments such as telescopes could reduce the force of the sceptical critique. With the naked eye (to take a familiar sceptical example) we are uncertain as to the real size of the sun: but the degree of magnification provided by a telescope gives us new information about the way we perceive the world, and makes the senses’ fallibility much less of a practical problem. This seems to have been Boyle’s view also, and it was well expressed by his friend and assistant Robert Hooke. The central question about the Hobbes-Boyle controversy is then: why did Hobbes treat Boyle so harshly and yet Gassendi so gently?

Shapin and Schaffer do not directly provide an answer to this question: indeed, Gassendi hardly figures in Leviathan and the Air-Pump. But the obvious answer is provided by what they have to say on the question of authority. Hobbes’s Dialogus physicus begins with an attack on the exclusivity of the ‘Greshamites’ (that is, the philosophers meeting at Gresham College, the Royal Society), and there can be little doubt that it was their formal recognition as a royal society in November 1660 which occasioned his attack. Since the time of Leviathan, Hobbes had been concerned with the problem of who should be publicly authorised to pronounce on philosophical matters. In that work he had abandoned an earlier willingness to see an authoritative church operating with the sovereign’s permission, and had argued strongly for the complete absence of any central philosophical or religious authority in the state. The sovereign must police ideas which might prove destructive to the community, but otherwise there should be no institutional support for a particular philosophical position. In Chapter 47 of Leviathan he told the story of the ‘unravelling’ of ecclesiastical authority and urged that no man ‘endued with Reason of his own’ ought ‘to follow the Reason of any other man, or of the most voices of many other men’.

The Restoration, as Shapin and Schaffer emphasise, saw Hobbes’s own intellectual liberty threatened by the renascent Anglican Church: and it was in the very year in which he was most under attack by Anglicans that he published his critique of Boyle. (In a second edition of 1668 he said of the Fellows of Gresham: ‘all of them are my enemies. One part of the clergy compelled me to flee from England to France: and another part of the clergy compelled me to flee back from France to England.’ These were first the Presbyterians in 1640 and second the Anglicans of the royal court-in-exile at Paris.) The Royal Society saw itself as compatible with the Restoration Church, and Hobbes obviously felt that philosophical liberty was threatened by both. This would not have been the case if they had taught his own philosophy, precisely because his philosophy, implemented properly, would have dissolved both institutions. The Royal Society might have come close in some respects to his views, as we have seen and as his friend John Aubrey was always aware, but its institutional existence was anathema to him. This, incidentally, is surely the principal reason for his non-membership, an issue discussed very well by Shapin and Schaffer.

Finally, what does the Hobbes-Boyle controversy tell us about modern science? Locating it as a controversy among post-sceptics helps to point up its continued significance for us, as both Hobbes and Boyle appear to have shared the fundamental assumptions of our current scientific culture; but practising scientists today, perhaps because of the continued existence of the Royal Society and of comparable other bodies, tend to line up with Boyle as a kind of establishment. It is to Feyerabend (who does not appear by name in Leviathan and the Air-Pump – just as Hobbes did not appear by name in many late 17th-century works, and yet brooded over them) that we must now go to hear something of Hobbes’s tones. ‘The separation of state and church,’ Feyerabend wrote, ‘must be supplemented by the separation of state and science, that most recent, most aggressive and most dogmatic religious institution.’

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