It is also a very curious thing. Why should a 17th-century Portuguese-Jewish philosopher whose dense and opaque writings are notoriously difficult to understand incite such passionate devotion, even obsession, among a lay audience in the 21st century? Part of the answer is the drama and mystery at the centre of his life: why exactly was Spinoza so harshly punished by the community that raised and nurtured him? Just as significant, I suspect, is that everyone loves an iconoclast – especially a radical and fearless one that suffered persecution in his lifetime for ideas and values that are still so important to us today. Spinoza is a model of intellectual courage. Like a prophet, he took on the powers-that-be with an unflinching honesty that revealed ugly truths about his fellow citizens and their society.

Spinoza is a role model for intellectual opposition to those who try to get citizens to act contrary to their own best interests

Much of Spinoza’s philosophy was composed in response to the precarious political situation of the Dutch Republic in the mid-17th century. In the late 1660s, the period of ‘True Freedom’ – with the liberal and laissez-faire regents dominating city and provincial governments – was under threat by the conservative ‘Orangist’ faction (so-called because its partisans favoured a return of centralised power to the Prince of Orange) and its ecclesiastic allies. Spinoza was afraid that the principles of toleration and secularity enshrined in the founding compact of the United Provinces of the Netherlands were being eroded in the name of religious conformity and political and social orthodoxy. In 1668, his friend and fellow radical Adriaan Koerbagh was convicted of blasphemy and subversion. He died in his cell the next year. In response, Spinoza composed his ‘scandalous’ Theological-Political Treatise, published to great alarm in 1670.

Spinoza’s views on God, religion and society have lost none of their relevance. At a time when Americans seem willing to bargain away their freedoms for security, when politicians talk of banning people of a certain faith from our shores, and when religious zealotry exercises greater influence on matters of law and public policy, Spinoza’s philosophy – especially his defence of democracy, liberty, secularity and toleration – has never been more timely. In his distress over the deteriorating political situation in the Dutch Republic, and despite the personal danger he faced, Spinoza did not hesitate to boldly defend the radical Enlightenment values that he, along with many of his compatriots, held dear. In Spinoza we can find inspiration for resistance to oppressive authority and a role model for intellectual opposition to those who, through the encouragement of irrational beliefs and the maintenance of ignorance, try to get citizens to act contrary to their own best interests.

Spinoza’s philosophy is founded upon a rejection of the God that informs the Abrahamic religions. His God lacks all the psychological and moral characteristics of a transcendent, providential deity. The Deus of Spinoza’s philosophical masterpiece, the Ethics (1677), is not a kind of person. It has no beliefs, hopes, desires or emotions. Nor is Spinoza’s God a good, wise and just lawgiver who will reward those who obey its commands and punish those who go astray. For Spinoza, God is Nature, and all there is is Nature (his phrase is Deus sive Natura, ‘God or Nature’). Whatever is exists in Nature, and happens with a necessity imposed by the laws of Nature. There is nothing beyond Nature and there are no departures from Nature’s order – miracles and the supernatural are an impossibility.