In the 18th century, many thinkers across Europe began to question the dogmas and authority of state-sanctioned religion and to hold up the virtue of reason as an alternative to superstition. ‘Superstition sets the whole world in flames, philosophy quenches them,’ wrote the French writer Voltaire, one of the leading figures of the loose intellectual movement called the Enlightenment.

The achievements of scientists such as Isaac Newton and the writings of the English philosopher and political theorist John Locke (see here and here ) were both influential. Newton and Locke embraced empiricism, the belief that knowledge derives from observation and experience, not from innate ideas. The former is the realm of reason, Locke held, while the latter is the realm of faith. Everything is up for question, all assumptions must be critically examined.

The thinkers of the Enlightenment sought to establish a rational basis for all human knowledge and action, from economics and the law to psychology, education and history. Although few were out-and-out atheists, many subscribed to deism, which restricts the role of God to the ‘first cause’ of the universe. In France these thinkers were known as the philosophes , and included such figures as Voltaire, Montesquieu and Denis Diderot (editor of the innovative Encyclopédie , ‘a reasoned dictionary of the sciences, arts and crafts’). A similar movement arose in Britain, particularly in Scotland, with figures such as the sceptical philosopher David Hume and the economist Adam Smith (see here ). All these figures are notable both for upholding the value of tolerance, and for their humanitarianism.

It took time for the values of the Enlightenment to be more widely adopted. Various European monarchs paid lip-service to the Enlightenment in the 18th century, but continued to rule as autocrats. The US Declaration of Independence of 1776 and the Bill of Rights of 1789 enshrine certain values of the Enlightenment, as does the Declaration of the Rights of Man and of the Citizen adopted in the wake of the French Revolution of 1789. However, the Enlightenment ideals of reason and tolerance still have not taken hold in many parts of the world.

The fate of free-thinkers

‘Écrasez l’infâme ,’ wrote Voltaire – ‘Crush superstition.’ He had in mind the treatment of those who would have considered themselves free-thinkers, but whom Church and state condemned as blasphemers. In 1697 an Edinburgh student called Thomas Aikenhead became the last person in Britain to be executed for blasphemy – he had called theology ‘a rhapsody of ill-invented nonsense’. In 2012, thirty-three countries around the world still had anti-blasphemy laws, and in a number of Muslim countries the penalty for blasphemy is death.

‘There is no effectual way of improving the institutions of any people but by enlightening their understandings.’

THE ENLIGHTENMENT