The Enlightenment

The model is the physics of Newton: a handful of mathematical laws accounts for the whole system of the world, with no occult qualities or providential ends. The Enlightenment turns this success into a universal method; what experimental reason has done for the heavens it can do for morals, politics and religion. No authority, tradition, custom or revelation is exempt from examination; everything must appear before the tribunal of reason. This is not yet the scientism of Comte, which will make positive science the only knowledge, but science here becomes the paradigm of legitimate knowledge and the lever of emancipation.

Sapere aude! Have courage to use your own understanding: this is the motto of the Enlightenment.An Answer to the Question: What Is Enlightenment?

Kant, What Is Enlightenment? · d'Alembert, Preliminary Discourse to the Encyclopédie

The movement defines itself by a wager: the spread of light emancipates, darkness enslaves. To dare to know, uproot prejudice, publish the Encyclopédie, is to hold that no moral or political progress can be bought at the price of maintained ignorance, and that tutelages live off the darkness they cultivate.

Kant, What Is Enlightenment? (1784) · The Encyclopédie (1751-1772)

Hostile to a priori systems and gratuitous hypotheses, the Enlightenment makes observation and experiment the source of all physics: one rises from facts to laws by induction, in the manner of Bacon, whom the Encyclopédie claims as its patron. Hume nonetheless radicalizes this programme by showing that induction itself is grounded not in reason but in habit. In parallel, the calculus of probabilities of Laplace and Condorcet opens a quantitative path to uncertainty.

Bacon, Novum Organum · Condorcet, Essay on the Application of Analysis to the Probability of Majority Decisions

The inaugural gesture is critical: against the dogmatism of school metaphysics and revealed truths, the task is to measure reason against its own limits. But this distrust is not the destructive scepticism of Pyrrho: Hume tempers his doubt into a mitigated, workable scepticism, and Kant turns it into a critique that bounds knowledge the better to ground it. Certainty now aims at what withstands examination, not at what imposes itself by authority, a fallibilist stance.

Kant, Critique of Pure Reason (preface) · Hume, Enquiry Concerning Human Understanding, sect. XII

The dominant epistemology of the philosophes is that of Locke: the mind is at first a blank slate, and all our ideas come from experience. Condillac draws from this a thoroughgoing sensationism in which even the operations of the mind reduce to transformed sensations. This empiricism feeds the critique of innate ideas, the supposed weapons of prejudice and authority. The current is not unanimous, however: a rationalist strand inherited from Descartes persists, and Kant will go beyond the alternative by showing that experience itself presupposes a priori forms of the understanding.

Locke, Essay Concerning Human Understanding, book II · Condillac, Treatise on the Sensations

From the accumulation of knowledge and the spread of enlightenment the current draws a new thesis: humanity advances, and that march can be conscious and willed. Institutions and laws are not sacred merely for being old; they must prove their present usefulness, failing which reform is legitimate. Condorcet pushes the idea to a law of history, the human mind progressing by stages toward truth, liberty and happiness. Against this creed Burke will set the accumulated wisdom of tradition: this is the birth certificate of the divide between progressivism and conservatism.

The perfectibility of man is truly indefinite; and the progress of this perfectibility has no other limit than the duration of the globe on which nature has placed us.Sketch for a Historical Picture of the Progress of the Human Mind (1795)

Condorcet, Sketch for a Historical Picture of the Progress of the Human Mind · Turgot, On the Successive Advances of the Human Mind

History ceases to be a succession of reigns or a decline from a golden age and becomes the directed development of reason. Condorcet divides it into ten epochs marching toward emancipation; Kant reads in it the unfolding, through the very « unsociable sociability » of men, of a design of nature toward a cosmopolitan society. Meaning is not conferred by an external providence but is immanent to the movement of societies, legible to whoever can interpret it. This philosophy of history will be inherited by Hegel and Marx.

Kant, Idea for a Universal History with a Cosmopolitan Aim · Condorcet, Sketch for a Historical Picture of the Progress of the Human Mind

Prior to all society and all positive law, man possesses as his own, by the mere fact of his rational nature, rights that no power has conferred and that none may legitimately abolish: to life, to liberty, to the property of his own person. Locke makes them the measure of every government, instituted only to secure them. These rights are universal because they flow from a common humanity, not from the privileges of an order or a birth: this is the weapon against absolutism and the society of estates, which the Declaration of 1789 will inscribe into law, « men are born and remain free and equal in rights ». Bentham, from within the century, will nonetheless object that a right without positive law is mere « nonsense upon stilts ».

Being all equal and independent, no one ought to harm another in his life, health, liberty, or possessions.Second Treatise of Government, §6

Locke, Two Treatises of Government, II · Declaration of the Rights of Man and of the Citizen (1789)

If reason is one and everywhere the same, then the principles of justice hold universally, and not by divine decree or local custom. Morality is secularized: it no longer depends on a revelation but rests on reason or on sentiments common to all men, which makes it possible to judge established mores rather than submit to them. Kant will give it its most rigorous form, a moral law valid for every rational being. Yet the current carries its own limit within it: Montesquieu's attention to the diversity of laws according to climate and people opens the way to the relativism that will soon contest this universalism.

Kant, Groundwork of the Metaphysics of Morals · Montesquieu, The Spirit of the Laws, book I

Political society is not a natural order or one willed by God, but a human institution born of the agreement of individuals: its sole source of legitimacy is the consent of the governed, not force, tradition or the divine right of kings. Locke makes it a revocable pact that the people may renounce if power betrays its end; Rousseau seeks the form in which, uniting with all, each « still obeys only himself » and remains free. Against this founding fiction Burke will set the organic community, inherited rather than contracted: but it is contractualism that gives the age of revolutions its grammar of legitimacy.

Man is born free, and everywhere he is in chains.The Social Contract (1762), I, 1

Rousseau, The Social Contract · Locke, Two Treatises of Government, II

Against divine-right absolutism, the Enlightenment advocates not the absence of power but its limitation by law. Montesquieu supplies the mechanism: for « power to check power », the legislative, executive and judicial must be separated and balanced. Liberty is not release from all authority but the security afforded by good laws. The century is nonetheless crossed by a tension: from Voltaire to Diderot, several philosophes also look to the reforms of an enlightened despot, not always with a constitutional guarantee.

Montesquieu, The Spirit of the Laws, book XI · Voltaire, Philosophical Letters

A citizen of the world before being a citizen of his city, the man of the Enlightenment claims a belonging that overflows borders and confessions. Reason and humanity being common to all, national and religious particularisms weigh less than what unites the human race. Kant draws from this a project of cosmopolitan right and « perpetual peace » among nations; the Republic of Letters already offers its lived figure, a learned community without a homeland. This cosmopolitanism nourishes the critique of war, slavery and fanaticism.

Kant, Toward Perpetual Peace · Voltaire, Philosophical Dictionary, art. "Fatherland"

Beccaria shifts punishment from the register of expiation to that of social utility: the penalty should not avenge the crime or satisfy a retributive justice, but prevent it. From this flow his reforms, the abolition of torture and the death penalty, the proportion of penalties to offences, the certainty rather than the cruelty of punishment, and prevention through education and good laws. Punishment is measured by its effects on the social body, not by the moral evil committed: a reforming programme that utilitarianism will take up.

Beccaria, On Crimes and Punishments (1764)

The political liberty of the century comes in several voices. For the liberal strand descended from Locke, it is first of all negative: a sphere of security and property in which the individual is unhindered. For Montesquieu, it is non-domination, « the right to do everything the laws permit », secured against arbitrariness by the separation of powers. Rousseau proposes its positive version, the autonomy of a people that gives itself its own laws. These distinct, sometimes rival accents share the refusal of arbitrary subjection.

Montesquieu, The Spirit of the Laws, XI, 3-6 · Rousseau, The Social Contract, book I

Against the dogma of original sin, which makes man a corrupt creature to be redeemed, the Enlightenment wagers on his perfectibility: his vices owe less to his nature than to bad institutions and to ignorance. If the mind is a blank slate, then education can do almost everything, holds Helvétius: change the laws, the enlightenment and the mores, and you change men. Rousseau radicalizes the wager, man being naturally good and corrupted by society, while Voltaire, more sombre, keeps it within measure. Hence a tempered optimism, founded not on what man is but on what he can become.

Helvétius, On the Mind · Rousseau, Discourse on the Origin of Inequality · Locke, Some Thoughts Concerning Education

The Encyclopédie performs an unprecedented gesture: bringing the mechanical arts, the trades and the machines into knowledge, on an equal footing with the sciences. Technology is here no mere convenience but a vehicle of emancipation, which lifts man out of misery and need and extends his dominion over nature. Heirs to Bacon's programme, the Enlightenment ties the progress of the arts to the progress of enlightenment: mastering nature and instructing men go together.

Diderot and d'Alembert, Encyclopédie, art. "Art" · Bacon, Novum Organum

In the wake of Bacon and Descartes, the current treats nature as a field to be known in order to master it and put it at the service of man: knowledge is power, and the progress of the sciences is worth the ills it relieves. Yet this conquering anthropocentrism is not without counterpoint: Rousseau already contests the idea that the arts and the domestication of the world have made us better, opening a critique that will only ripen later.

Bacon, Novum Organum, book I · Buffon, Natural History

The Newtonian universe lends itself to a mechanist reading: a system of bodies in motion governed by laws, without ends or souls. La Mettrie draws the extreme consequence with « man a machine », and the materialism of d'Holbach reduces everything to matter and motion. The century is not mechanist without remainder: Diderot and the naturalists grant matter a sensibility and activity of its own, the sketch of a vitalism, while a deist finalism persists that reads in the order of the world the mark of a great clockmaker.

La Mettrie, Man a Machine (1747) · d'Holbach, The System of Nature · Diderot, D'Alembert's Dream

On religion the current makes common front even where it diverges about God: reason, not revelation or the Church, is judge in the last instance. Many hold revealed religion to be incompatible with it, mixed with superstition and fanaticism: it is the « Infamous Thing » that Voltaire would « crush ». Others substitute for it a natural religion, or deism, attuned to reason: a clockmaker God without miracles or clergy. From this primacy follow the cardinal demand of tolerance and the separation of the civil from the religious: Locke shows that no one can be compelled to believe, and that salvation is no concern of the State.

Voltaire, Treatise on Tolerance · Locke, A Letter Concerning Toleration