This essay, on John Locke, Baruch Spinoza and the meaning of tolerance, was my Observer column this week. (The column included also a short piece on politics as drama.) It was published on 8 September 2019, under the headline ‘Why western liberals have long picked the wrong historical hero’.

Lost in the library of a small American college has lain a text by one of England’s foremost philosophers that no one knew he had written. ‘Reasons for tolerateing Papists equally with others’, a work by the early Enlightenment philosopher John Locke was discovered in the archives of St John’s College in Annapolis, Maryland, by the independent scholar JC Walmsley. The find, announced last week, has been greeted with excitement by both philosophers and historians. It is significant, too, in throwing light upon political debates that have as much relevance now as they did 400 years ago.

Locke is central to modern politics because of his foundational role in liberalism. His Two Treatises on Government was highly influential in the development of liberal democracy. A Letter Concerning Toleration, published in 1689, is a key text in furthering notions of free speech and religious toleration. Both works shaped the thinking of Thomas Jefferson and other leaders of the American Revolution and underlay their commitment to the separation of church and state.

The proper concern of government, Locke argued in A Letter Concerning Toleration, is the protection of life, liberty, health and property. The state should not be concerned with an individual’s religious beliefs or his means of salvation.

Written at a time when Europe was rent by religious strife, and when intolerance and persecution were the norm, it was a powerful argument for religious freedom. It was, however, also a narrow conception of liberty. Locke’s aim was to extend freedom of worship to nonconformist Protestant congregations. Neither Catholics nor atheists were, in his view, deserving of tolerance, the former because they gave their allegiance to a ‘foreign prince’ (the pope), the latter because their opinions were ‘contrary… to the preservation of civil society’.

And here lies the significance of the newly discovered document. Written some 20 years before A Letter Concerning Toleration, its very title cuts against the grain of much of what we know of his thought.

‘If Papists can be supposd to be as good subjects as others,’ he writes, ‘they may be equally tolerated.’ This has led many scholars to suggest, like Walmsley, that Locke was ‘much more tolerant in certain respects than was ever previously supposed’.

That seems doubtful. What the new manuscript shows was that Locke was aware of the arguments for religious freedom being extended to Catholics but in his published work he rejected them. Catholics were not ‘as good subjects as others’ because their beliefs threatened society and so had to be excluded.

This blindness to the meaning of tolerance was not peculiar to Locke. The question of what, and who, should be tolerated has been a fraught issue for liberal thought over four centuries. Today, anti-Catholic bigotry has largely faded. But Jews and, more recently, Muslims have faced the same argument that once applied to Catholics – that they have a ‘dual loyalty’ and that their beliefs threaten society.

Today, too, the question of what we should tolerate is as contested as it was in Locke’s time. From sedition to hate speech, from fake news to the giving of offence, there is a plethora of arguments about the need to constrain speech so as not to harm society, arguments that are often as hollow as Locke’s.

The Enlightenment thinker who adopted a truly liberal attitude towards toleration was not Locke but the Dutch philosopher Baruch Spinoza, whose work is far too little known, especially in the Anglophone world. Locke, as the historian Jonathan Israel has sketched out in a series of monumental books, was a key figure of the ‘mainstream’ Enlightenment, while Spinoza was a guiding light of the ‘radical’ wing. The mainstream, Israel suggests, was constrained in its ability to critique laws and conventions by its intellectual and social timidity. The radical Enlightenment was far less willing to compromise its beliefs about toleration, democracy and equality.

This distinction is particularly visible on the question of freedom of expression. ‘The less freedom of judgment is granted to men,’ Spinoza said, ’the further are they removed from the most natural state and consequently the more repressive the regime.’ Involvement by the state, he insisted, ‘should be restricted to men’s actions, with everyone being allowed to think what he wishes and say what he thinks’. It is a view that seems startling even today.

So, let us celebrate a great historical find in the new Locke manuscript. But if we want to address questions of tolerance we would do far better to look to Spinoza than to Locke.