1. René Descartes made a profound observation, 'I think, therefore I am.'
2. That the fact we think indicates we exist, and the rest must be doubted.
3. Descartes used the concept of vision to further illustrate the point of view.
4. He sketched a diagram showing how vision was mathematically possible.
5. He showed light entering the eye as rays of lines and converging at the back.
6. But this wasn't seeing, observed Descartes, rather it's the sense of judgement.
7. In the sense we see what there is to be seen, then come to a decision about it.
8. So the concept of vision, from this illustrative pov, represents the role of a judge.
9. And just as a judge decides based on the evidence, seeing is based on evidence.
10. In doing so, Descartes raised the importance of seeing as observed experiments.
11. At the same time, science learned to differentiate biological from cultural judgement.
12. Biological sight: what there is to see; cultural judgement: making sense of what we see.
13. Or that seeing the world isn't about how we see, but about what we make of what we see.
14. Ludwig Wittgenstein's duck-rabbit drawing is an example to help us imagine the difference.
15. Wittgenstein's duck-rabbit drawing can look like a duck or a rabbit based on how you see it.
16. This is because there are two streams of brain activity: one for perception, other for action.
17. And so what we make of what we see is a complicated interaction between the two streams.
18. Or, as the art professor Nicholas Mirzoeff notes, that the brain isn't a camera, but a sketch pad.
19. So seeing doesn't happen, it's something we do; and it takes brains to see, beyond a pair of eyes.