In an interview on The Enlightenment

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.