We were going to talk about sexual customs in the Enlightenment, but I notice that of the books you’ve chosen only one, the last, actually seems to deal with sex at all. Instead you’ve given us a look at the Enlightenment as a sort of slow-breaking social revolution – a revolution which is still breaking – starting with Isaac Newton’s Opticks, first published in 1704.

Yes I put those books in an order – not really an historical order, nor precisely thematic – more a way of describing how I’ve come to think of the Enlightenment. Some of the ways in which I think it’s interesting.

Newton’s Opticks seems a good place to start because it’s about light.

Exactly, and about seeing. And the idea of light and vision seem to me to be behind the fundamental breakthroughs of the Enlightenment. They can be taken as the principles or the maxims of almost all moments in intellectual history where people see themselves undergoing a revolution or transformation. The idea that you are seeing something familiar differently, even as capable of changing the world, seems to be the essence of all intellectual and social revolutions. So we’re taking the Enlightenment here as the single most important of all intellectual revolutions in the West and I picked Isaac Newton’s Opticks as my first text in order to flag the main themes of this revolution.

Your first pick was the Opticks but you wanted to draw our attention particularly to a later addition to the Opticks known as the ‘Queries’.

Yes. Newton’s a genius whose most obvious contribution to science was to formulate the laws of thermodynamics and to come up with breakthrough theories about light, colour, vision and so on. But in the Queries to the Opticks he treats these questions as philosophical problems as much as scientific problems. He sees his work not simply as changing the way that scientific inquiry is going to happen for the next 300 years, but also the way that people think about what it means to be human. So if we’re using optics as a key figure for how people think about revolution then Newton gives us another word: ‘Query’, the idea of questioning, investigating, of opening up problems to people at large.

Which is perhaps why you chose John Locke’s Essay Concerning Human Understanding as your next book? Published slightly before the Opticks in 1690.

Locke’s a very interesting figure in many of the same ways that Newton is. They’re both coming out of a century of revolution and dissent in England; a century in which the church and the state have been questioned in the most profound ways. A century in which absolutism has been seen as an insupportable political position, where the old regime government in Britain was no longer viable. The 17th century saw a dawning of parliamentary government, and a commitment at least to popular social participation in the life of the state. That’s the political backdrop against which both of these men are working. Locke’s a political philosopher, Newton’s a natural philosopher or scientist. But really both of them were responding to this idea of popular participation, the will of the people, as a way to think about philosophy and science in radically different ways. Newton’s work on vision and light and sight and Locke’s ideas about the emotions and the mind establish the consciousness and perceptions of the individual at the centre of human life. It’s a secular view. So instead of a supreme, authoritative, monarchic figure being the presence that describes what power is like in the world, the authority of the individual takes over. Newton establishes the validity of human perception, Locke establishes the validity of individual consciousness. And these two things, the ability to see or think authoritatively really become the cornerstones of the Enlightenment, and from there of all modern thought. They establish the individual at the centre of collective life.