The idea that we have evolved to see reality ‘as it is’ is commonplace. While it might seem irresponsible, in this age of ‘fake news’ and ubiquitous political and commercial propaganda, to argue that we are not evolved to see reality as it is, I believe it’s worth doing, not least for what it reveals about our notions of ‘reality’ and ‘evolution’.

Pioneering vision scientist David Marr, for example, explained in his 1982 book Vision that ‘one interesting aspect of the evolution of visual systems is the gradual movement toward the difficult task of representing progressively more objective aspects of the visual world’.  Almost every textbook agrees. Seeing the world as it is, objectively, is widely assumed to make organisms better able to find food, avoid predators or other dangers, fend off rivals, and mate successfully; it is, in other words, widely assumed to render organisms better adapted to their environments.

Evolution favors better-adapted organisms, so evolution should favor an ability to see the world objectively. What, after all, could be the advantage in not seeing – in general, sensing – the world correctly? Evolution must make organisms progressively better at sensing their worlds. How could anyone disagree?

Reality would be subjective if it is only 'in the mind of the perceiver'. But does the moon exist only when you look at it? 

As in any philosophical debate, disagreement starts by asking what words mean. Let’s start with ‘objective’. Reality is objective if it is independent not just of my observations, but of your observations and everyone else’s observations. It is there, just as it is, whether anyone is looking or not. Reality would be subjective if it is only ‘in the mind of the perceiver’. Einstein is often quoted as asking Abraham Pais whether he ‘really believed that the moon exists only when I look at it’. If the moon is objective, it exists even if no one is looking at it.

Have we evolved to see an objective reality? What would an objective reality look like? The obvious place to turn is physics. In Newton’s time, a physicist might have answered confidently about planets and cannonballs, a bit less confidently about heat and light, and with a look of perplexity about gravity.   Fast forward a century and electricity and magnetism have entered the mix. Fast forward another century and we have atoms: indivisible hard spheres spinning in the void. Plus light, now a mysterious combination of electricity and magnetism. And gravity is still a complete unknown.

Move into the twentieth century and the answers rapidly leave the realm of ordinary experience altogether, encompassing quantum fields and black holes. Physicists disagree about what the basic terms in their theories even mean. Many hold that the world of ordinary experience is an illusion. By the start of the twenty-first century, some physicists soberly claim that reality consists completely of information (see my ‘Sciences of observation’ for a history of this development).

There is a trend here, and it is not encouraging for the claim that we evolved to see reality. We evolved to see rocks and rivers, plants and animals, and especially other people. Physics has nothing much to say about these things. The reason is simple if somewhat subtle; neither quantum nor classical physics provides any principled means for saying what counts as an object (an entity with a boundary in space and an identity through time).

If we evolved to see reality, we evolved to see only a tiny slice of it.