What, exactly, do philosophers do?

What, exactly, do philosophers do? Are they primarily engaged in inward-looking technical debates, or are they the leading innovators who frame wider projects? In this elegantly written and insightful survey of selected thinkers from Hobbes and Descartes to Voltaire and Rousseau via Spinoza, Locke, Bayle, Leibniz and Hume, Anthony Gottlieb argues for their key role in the formation of the Enlightenment. As an exercise in making philosophical writing widely accessible, this is a blast of fresh air; better still, the volume is one of a trilogy, following his widely praised The Dream of Reason (2001), and we have one more to come. But that putative outcome may be questioned.


Communicators of genius have organizing frameworks too. In Gottlieb’s account, this 150-year “staccato burst” of European philosophy was a response to two leading stimuli: “Europe’s wars of religion and the rise of Galilean science”. This phase (one of only two in philosophy’s history, he claims) happened when some people began to criticize “the ancients” and “the authority of the Church”. Such is the book’s explanatory structure; yet on closer examination Gottlieb’s thinkers partly fit his model, partly not. Descartes, for example, is presented as saying nothing of the wars of religion that had torn Europe for a century, and was “apparently untouched by any doubts about the main dogmas of the Catholic Church”.


The new science is central to this book, but proves to be a source of contention as well as of common cause. Leibniz later thought Descartes’s four rules of scientific method, writes Gottlieb, “so vague as to be almost vacuous”. Gottlieb quotes Descartes’s words that “in many cases the grasp of the senses is very obscure and confused”. Despite Voltaire’s praise, Locke’s empiricism is not, for Gottlieb, the unchallenged key to the Enlightenment: empiricists disputed with rationalists (a “vague and confusing” distinction anyway) at least until Kant, and many philosophers, like Hobbes, Spinoza and Leibniz, did not see the problem of knowledge as central. Descartes’s arguments for the existence of knowledge depend on his arguments for the existence of God; yet “his theological arguments are flimsy”. Nor was Descartes a social campaigner. The rights of women, like other political topics, did not interest him. “He had focussed more on the general nature of knowledge than on any social consequences of enlightenment.”

As for Hobbes, Descartes condemned the tendencies of his teaching, despite Hobbes being a supporter of the “new philosophy”, but Hobbes took materialism far beyond Descartes. Though profoundly interested in politics, Hobbes made common cause with nobody and had few followers (no Enlightenment project there; indeed, Diderot condemned him). Hobbes, cautions Gottlieb, did not set out to provide “a purely secular understanding of politics”, although he clearly satisfied Gottlieb’s criterion of seeking to provide a remedy for religious war. Hobbes was making “a purely technical point” in arguing that the sovereign could do no wrong, since he was arguing deductively from definitions. He met Galileo in 1636, embraced the “mechanical philosophy” and used it as a model for politics, but his deduction emerges here as far more important than his mechanics.


Locke and Hume, argues Gottlieb, echoed Hobbes even as they distanced themselves from him (not always successfully). Locke, for example, wrote in the same terms as Hobbes about free will. But Hume’s Treatise of Human Naturedid not follow Hobbes’s Leviathan in the latter’s attention to religion. We might add that Hume’s work sought to reconcile dynastic conflict, not wars of religion. Gottlieb rightly defends Hobbes from the charge of atheism, but can hardly do the same for Hume.


Spinoza, by contrast, had problems with the Portuguese Synagogue at Amsterdam, which expelled him. But Gottlieb asserts Spinoza’s theism in the context of a discuss­ion of his attachment to the new science: “Spinoza can be seen as carrying the message of the mechanical philosophy beyond the confines of physics into the new territory of religion and ethics”. Indeed, he published a respectful commentary on Descartes’s philosophy that pushed its ideas, in some ways, further. But Gottlieb judges that Hobbes, and to a lesser extent Spinoza, did themselves harm by seeking to copy Euclidian geometry as a model of philosophical demonstration. Arguments that God is in some sense the same as nature, although not exactly what Spinoza said, proved problematic both as physics and as a means of religious reconciliation. Spinoza’s practical concern was also with the inner conflicts of his Marrano community, not the wars of Protestant and Catholic or the theological controversies sparked by Luther or Calvin. While advocating religious toleration, Spin­oza taught the necessity of political intervention to sustain a state Church, supported to advance “public peace and well-being”. The national religion was to be “of a most universal nature”, and, presumably, enforced by the state. After all, Spinoza “thought he already knew what the best sort of life consists in”.


Gottlieb takes Locke’s attack on innate knowledge to be a commonsensical foundation of “British empiricism” rather than the political point it was (that is, a critique of royalists’ claims that monarchical allegiance was natural or innate); he believes that “in questions of religion, Locke’s leading idea was that theological doctrines must be answerable to the court of reason” without noting that Locke approved a priori of some forms of religion and disapproved of others. For that reason, we might add, Locke could offer no solution to the conflict of religions. Gottlieb tells us that “Newton and Locke were often pronounced to be the twin prophets of the Enlightenment”, but without noting that this happened very much later, and without offering any evidence of Locke’s supposed role.


Instead, we learn in conventional terms that Locke was just one of those who protested against Charles II’s “Catholic absolutist ambitions” with “vigorous defences of political freedom”. Just how Locke’s politics related to his epistemology or to his interest in the new science we never learn. Gottlieb hints that some of Locke’s political ideas (we do not learn which) may have been “stolen” from his friend James Tyrrell. He adds that Locke’s theory that the legitimacy of government depends on an original contract fails since it would have been, in Hume’s words, “obliterated by a thousand changes of government and princes”. According to Locke, men entered into civil society to protect their property. But, Gottlieb objects, Native Americans did no such thing.


Locke’s claim to have fathered the Enlightenment rests chiefly on his Essay Concerning Human Understanding, “rightly seen as an ambitious elaboration and extension of the ‘new philosophy’ of Galileo, Descartes, Newton and the Royal Society”. But was it? The famous objection that Locke’s Two Treatises of Government depends on natural law, but that the Essay denies innate ideas (by implication including natural law) is not examined. No Enlightenment project here either, then.


Pierre Bayle argued, in Gottlieb’s words, both that atheism would not cause the disintegration of society and that “the persecution of heresy” would cause “endless bloodshed”. But Bayle, too, “had reservations about Catholics”, so that, we might infer, religious peace depended on Catholics not being tolerated. This would not easily bear out Bayle’s reputation of being “something of a Socrates to those thinkers in the eighteenth century and beyond who thought of themselves as enlightened”.


Leibniz, a scientific polymath, can hardly be bettered as a practitioner of the new science, but he was also the author of an unpublished book-length critique of Locke’s Essay. In turn, his argument that this is the best of all possible worlds incurred Voltaire’s satire. Leibniz was also fearful that the new science would threaten, in his words, “the certainty of an eternity after death”; he wrote a work against the implications of Spinoza’s Ethics and another against Bayle’s ideas of theodicy, which shows little sense of common cause. He pursued, in religion, a “project of universal reconciliation”, but it is not clear how many of his contemporaries noticed. His employer the Elector of Hanover, when he became George I, refused him permission to move to England, perhaps because Leibniz was attacking Newton’s ideas as “in effect, an insult to God”.


The scenario with which the book opens seems seldom appropriate except on the old premiss that Churches and monarchs were all superstitious and stupid, which hardly squares with the Lutheran Leibniz’s relations with his princely patrons. For Hume, religion was “a phenomenon to be explained in psychological and historical terms”, writes Gottlieb. But although Hume clearly did see himself breaking the shackles of Christian superstition, he did not do so by forging any alliance with natural science. Rather, for Hume the central issue was “the problem of induction”, and here he concluded that we are led not by reason or science but by custom; as he wrote, “divinity and school metaphysics” were only “sophistry and illusion”.


Instead of a Conclusion, Gottlieb offers a chapter on Voltaire and Rousseau. But this is not exactly a culmination. True, no more sarcastic opponent of the French Church could be found than Voltaire, and Rousseau admired only “the religion of the Gospel pure and simple”. But neither derived their stances on religion from any significant knowledge of the new science, however much Voltaire praised Bacon, Galileo and Descartes as enemies of superstition. Rousseau, indeed, condemned the sciences as “futile in the objects they propose” and “dangerous in the effects they produce”. Technological inventions were often harmful (printing, for example, which spread the “pernicious reflections” of Spinoza). Philosophy was as bad, continued Rousseau: “the reasoning and philosophic spirit . . . quietly saps the true foundations of every society”. Better far for man were “ignorance, innocence, and poverty”.


Rousseau also hated Voltaire and fell out spectacularly with Hume. Where, then, was the consensual Enlightenment project? Towards the end, the book limits its ambitions. The philosophes increasingly stressed human limitations: rather than the Age of Reason, “‘The Age of Trying to Be More Reasonable’ would therefore be a more accurate, though less snappy, name for their times”. It is a limp conclusion, despite Gottlieb’s fervent final championing of “The case for the Enlightenment” in the singular.


Why, then, did this array of outstanding thinkers write as they did? Perhaps such leaders were primarily preoccupied with those high-level debates on abstractions after all: Descartes’s vortices, Leibniz’s monads; Locke’s original contract, Priestley’s phlogiston. Perhaps their religious and political preferences were not determined by their philosophical methodologies? Anthony Got­t­lieb’s skill lies in making these debates both intelligible and enjoyable, but what did they amount to in the end? Are philosophers really so useful? Did even this remarkable team actually manage to frame “the Enlightenment”? Gottlieb’s very lucidity of prose and of intellect leaves us with more doubts, not fewer.