Joseph Wright of Derby’s ‘A Philosopher Lecturing on the Orrery’ (c1766)
Joseph Wright of Derby’s ‘A Philosopher Lecturing on the Orrery’ (c1766) © Derby Museum and Art Gallery, UK/Bridgeman Images

Sixteen years ago, Anthony Gottlieb published the highly acclaimed The Dream of Reason, taking us from Ancient Greece to the Renaissance in what was to be the first of a two-volume history of philosophy. The Dream of Enlightenment is not quite the long-awaited sequel, since it only advances to the middle of the 18th century. Based on the evidence so far, however, even if the third volume does not appear for another 16 years it will be worth the wait.

Gottlieb avoids the “learned Gibberish” John Locke lambasted, written by scholars who “cover their Ignorance with a curious and unexplicable Web of perplexed Words”. Instead, he wears his learning lightly with an engaging and entirely comprehensible sequence of crystal-clear paragraphs. As a former executive editor of the Economist, Gottlieb remains true to the journalistic values he learnt there, which he once described as the need to be “both Kosher and intelligible”.

His prose is as witty as it is punctilious, peppered with clever, memorable lines. For instance, writing about the argument that God’s goodness ensures we are not systematically deceived in our perceptions, he says: “God’s guarantee is not worth the paper Descartes wrote it on.” Not even Gottlieb could remove my deafness to the appeal of Gottfried Wilhelm Leibniz, but his beguiling chapter on the German thinker did at least persuade me that he was “the greatest polymath since Aristotle” and “there has not yet been a third person who can stand alongside them”.

As a scrupulous fact-checker, Gottlieb rejects many of the unjustified canards that fill too many introductions to philosophy. One of the greatest of these is that the philosophers of the modern era can be neatly divided into rationalists such as René Descartes, Leibniz and Baruch Spinoza, who favour pure, abstract reasoning over evidence, and empiricists such as Locke, David Hume and George Berkeley, who prefer the evidence of the senses over the detached calculations of the mind.

In fact, the Englishman, the Scotsman and the Irishman who represent Team Empiricist were a diverse trio, and Berkeley “saw himself as above all an opponent of Locke’s, not as a teammate”. Descartes was a keen experimenter who would visit butchers’ shops “to fetch carcasses for dissection”, while Spinoza was not only a lens grinder, but “conducted experiments in hydrodynamics and metallurgy”.

Front cover of 'The Dream of Enlightenment', by Anthony Gottlieb

This is not the only way in which present-day framings lead us to misunderstand the philosophers of the past. The fact that they still seem so relevant fools us into thinking that “they speak our language and live in our world”. Gottlieb succeeds in the task he sets himself to place these thinkers in their contemporary context.

Theirs was a time of an optimism so unprecedented that the word didn’t even exist until coined by a reviewer to describe Leibniz’s belief that we live in the best of all possible worlds. Fuelled by the promise of Galileo’s new science, many believed that “surely the truth was now just around the corner”. In retrospect, this excessive faith in reason was more unjustified positive thinking than rational confidence. “Hobbes’s claim that a scientific grasp of human nature could put an end to most civil wars is in one respect even more extravagant than Descartes’s prediction that science would abolish all disease within his own lifetime,” writes Gottlieb.

However, Gottlieb has little time for those who would exaggerate the naivety that followed. He bats away the remarkably common claims that the Enlightenment is responsible not only for the French reign of terror but “fascism, communism, psychiatric malpractice, economic exploitation, sexism, the extinction of species, madcap utopian schemes, environmental degradation and much else”. Thomas Hobbes and Descartes might have had excessive expectations, but the philosophes “sought merely to press questions that seemed reasonable and necessary, and to do so with a sense of the limits of the human intellect”. We talk now of an “Age of Reason” but only, Gottlieb suggests, because “The Age of Trying to Be More Reasonable” loses in snappiness what it gains in accuracy.

No one better exemplifies this intellectual modesty more than Hume, who advocated basing the study of ethics, politics, aesthetics and what we would now call psychology on the careful observation of human nature. When we do this, he argued, we discover that we do not reason with the “subtilty and refinement of thought” assumed by most philosophers. Indeed, when it comes to understanding how the natural world works, we are guided more by habit and instinct than deductive reasoning. All science is a generalisation from limited experiences that cannot be justified by principles of logical inference: no truths about “all” strictly follow from observations of “some”.

This failure of scientific and factual reasoning to meet the standards of logical proof — the “problem of induction” — has bothered philosophers ever since. Many think it a kind of scandal that it cannot be solved and have portrayed Hume as a sceptic who leaves us stripped of all our reason. Gottlieb is careful to avoid this mistake. For Hume, the way we think about the natural world may not be logical, but it is “just”. “Experimental reasoning” is not deductive reasoning but it is still reasoning.

Because Gottlieb does not take an excessively idealistic view of the power of reason, he is able to put the achievements of the thinkers in this book in their place, neither exaggerating nor diminishing them. He is as crisp in his criticism of the thinkers he admires as he is of their shallower opponents. Descartes, he writes, “tried to work out too much in his head” and his “theological arguments are flimsy”.

Despite the many mistakes of the Enlightenment philosophers, Gottlieb makes a convincing case that it would be “churlish” to deny that in the battles for scientific progress and against excessive religious authority and unjust political institutions, they fought on the right side and “probably helped to win them”. We have to remember that they were from a time when Hobbes’s materialism earned him the nickname the “Monster of Malmesbury”, and when “Denying that there was such a thing as a witch was almost as bad as being one.” In helping us to understand these pioneers, Gottlieb has continued their work of making ours, if not the best of all possible worlds, then “an intellectually adventurous [and] a less ignorant one”.

The Dream of Enlightenment: The Rise of Modern Philosophy, by Anthony Gottlieb, Allen Lane, RRP£20/Liveright, RRP$27.95, 320 pages

Julian Baggini’s new book, ‘The Edge of Reason’, is published next month by Yale

Photograph: Derby Museum and Art Gallery, UK/Bridgeman Images

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