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Hello, in the collection of Cambridge University Library is a modest notebook which belongs

to Isaac Newton when he was a student.

As well as notes about the mathematical textbooks he was reading, it contains the detail of some of his earliest

experiments one of these which would horrify modern researchers entailed inserting

a knitting needle behind his eyeball to see what effect this had on his vision. Newton's dangerous

experiments were part of a two and a half thousand year quest to understand the

nature of human vision. Ancient thinkers were fascinated by the eye, believing it contained a mysterious illuminating fire.

In later centuries it became known, in Leonardo's famous phrase, as,

the window of the soul.

But establishing the structures and properties of the eye took many centuries on the work of some of the greatest figures of Western thought.

With me to discuss the history of the eye are Patricia Farrah, Senior Tutor of Claire College, University of Cambridge,

William Alyph, Gresham Professor of Physic at Gresham College,

and Robert Ilyph, Professor of Intellectual History and the History of Science at the University of Sussex.

Perusha Farah, who were the earliest thinkers to study the workings of the art that we know

about and in what context did they undertake that?

Well the first theories that we really know about were by the pre-Socratic in 5th century BC in Greece and one of

the most famous of these was Empedocles and their basic idea was that there's some divine fire

inside your eye that goes out and it's almost like the feeling of touch. You

stretch out your fingers to touch something and feel it and learn about it and similarly the fire goes out from your eye

and enables you to learn about what it is that's in front of you. And you can see relics of that idea in one English we talk about we say something like

...