Ard: I wanted to ask a question that I read on your blog recently. You talked about how colour is perceived, and this has to do, partially, with the way our brains are structured. So the structure to our brains allows us to see colour in certain ways, and then there’s also a structure to our brain that allows us to perceive mathematics in certain ways. And that’s clearly evolved over time.

SZ: Yes, well, look, I think we have to go a step back and ask, what is the function of the brain? Now, there are a lot of functions which you can impute to the brain – individual functions: seeing, hearing, working out solutions, acting and so on. But there is one primordial, overall function, which is to acquire knowledge about the world. Now, here is the most important philosophical question of all: to obtain that knowledge, you have to stabilise the world. You cannot obtain that knowledge unless you can stabilise it. Now, in colour vision, what does stabilising it mean? It means that you have to get rid of all the continual changes in the wavelength anti-composition of the light coming from surfaces. You have to discard these and assign a constant colour to a surface.

David: When you say ‘stabilising reality or the colour’, what do you mean by that?

SZ: Well, I’ll give you an example. If we look at green leaves in a park, we see these green leaves as green, at noon on a cloudy day or a sunny day. If you look at them at dawn or at dusk, you’ll still see them as green. If you were to measure the amount of red, green and blue light reflected from these leaves in these different conditions, you find vast differences, and indeed, at dawn and at dusk, they’ll reflect more red light.

Now, how does the brain stabilise the world so that you can see it only as green? It takes the amount of red, green and blue light reflected from that leaf, and the amount of red, green and blue light reflected from the surround. It takes those ratios – those ratios never change.

So whatever amount of green light this leaf is reflecting, the surround will always reflect less, because it’s got lower efficiency. And whatever amount of red light it’s reflecting, the surround will always reflect more because it’s got a higher efficiency. Now, there is no physical law which says that these ratios should be taken. It’s the brain’s law – it’s the brain’s way of stabilising the world in terms of colour.

David: So that we can always say, ‘Oh, that’s a leaf because it’s green’?

SZ: Yes, you can identify something by its colour, absolutely.

David: So, in some ways, we’re not making reality up, but we are imposing a, sort of, slightly artificial order on it.

SZ: No, no, no, no you are making reality up, in a way. The only reality that you can experience is what the brain allows you to experience. Now supposing that you did not have this ratio-taking mechanism in the brain, what will happen? Sometimes that leaf would appear red, sometimes it would appear green, sometimes it would appear blue, sometimes yellow. Then you would no longer be able to recognise it by its colour because you’ve not stabilised the world.

David: Which would be bad news if you fed on green leaves!

SZ: This would be bad news if you fed on green leaves, indeed. It would be very bad news.

David: If you got to a certain time of day and say, ‘My God, there’s not a leaf in sight!’

SZ: Yes, yes, so I think that this is another fundamental issue, which is that there is a reality out there and that we represent that reality, and we take part in constructing that reality. Our brain, through its laws, takes part in constructing that reality. And here in comes stabilising the world: the brain is able to stabilise that world, and acquire knowledge about it, and that’s the only way it can do it.

David: When you talk about stabilising the world, what struck me was that the brain must get a certain pleasure from doing that, because it makes sense of it, as you were saying.

SZ: Yes, yes.

David: And in some way, what you’re doing in science, at a sort of cognitive level, is you’re doing that same thing. You’re saying, here’s all of the confusion of the world, and I will stabilise it by saying, well, underneath this, there are these stable rules that allow me to understand all of it.

SZ: All these mathematical formulations which tell you about the structure of the universe are also an attempt, at a highly cognitive level, to acquire knowledge about the world. I mean, it would be correct, would it not, to say that the description of the structure of the universe is an attempt to acquire knowledge about it.

Ard: Yeah, that’s right.

SZ: Now, there are situations in which there are contradictions. For example, you know, the well-known optical illusion: the bi-stable figures.

David: Oh, the young woman/old woman or the duck/rabbit

SZ: Yes, duck/rabbit, that sort of thing, which you can illustrate. Now, there is no solution to this… there is no certainty as to which solution is the valid one, because there isn’t a valid solution. So what the brain does is very simple, it makes both solutions valid, but only one has the conscious state at any given moment: you cannot see them both. And what does the brain do when you’ve got the laws of gravitation conflicting with the laws of quantum mechanics? It treats them separately. So, it’s again using the same strategy of saying, look, they are both correct, but not at the same time.

Ard: So something which is very surprising about the laws of mathematics is that somehow our brain has evolved in order to understand these laws, apparently, but then it turns out these laws are deeply engrained in the universe. So why did our brains…?

SZ: Well, our brains have evolved in the universe, and they… This is not an easy question to answer, and I just do not know the direct link between the structure of the universe and the structure of mathematical formulae which reveal that structure of the universe. But what is evident is that there is a certain logical deductive system, which by the way is applicable in as much in mathematics as it is in the humanities, and to obtain… to stabilise the world, to obtain the knowledge, you have to obey that logical deductive system.

Ard: Do you think that suggests that that logical system might somehow be in the universe before our brains arrived?

SZ: I wouldn’t dare stick my neck out as much as that. But I would say that it is through that logical system that you derive knowledge about the universe, and hence the reality you create, and the reality that you know, is based on that system, and because that system is similar in most humans, you get this similar, kind of, reality. Now, yes, there are big differences – a Buddhist maybe thinking of things in different terms — but if you look at it very carefully, it boils down to essentially the same thing.

I’m not saying there’s no physical reality out there. I’m not saying there isn’t a universe. I’m not saying the Earth isn't round. I’m not saying any of these things. All I’m saying is that to obtain knowledge about that, we do it through our brain, and we use our brains’ mathematical, logical system to obtain that knowledge.

Now, it would be, to me, extremely interesting about certain kinds of knowledge which are not directly observable, such as the Big Bang, such as black holes, such as the fact the universe was a billionth of the size of an atom before the Big Bang. These are not directly observable by us: these are deductions arrived at by mathematical formulations.

I’m very interested to learn, and I’ve got no strong position on that, if a totally different logical system would have arrived at the same conclusion. Now, if it does, then my argument is completely null and void, on the other hand, if it does not, then you’ve got to concede that a significant part of our knowledge is based on the structure and functioning of our brains.

David: So it’s whether the lens that we look through reflects what’s out there, or somehow distorts it? Whether we look through a glass darkly or clearly?

SZ: Yes, yes, yes.