The Standing Invitation

Posts Tagged ‘Philosophy

No Nonsense

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Recently a copy of A J Ayer’s Language, Truth and Logic passed through S I Towers, and it caused quite a stir. It’s a short book and very readable – and, I was amazed to learn, was written when the author was younger than I am. It is a beautifully argued manifesto of logical positivism.

Philosophy, for most people, is the asking of Big Questions. Is there a god? What happens after we die? Does the world disappear when we close our eyes? What is ‘truth’? What is ‘good’? And these questions are called Big Questions precisely because thousands of years of arguing have got us no closer to answering them.

Logical positivism was an attempt to tackle these issues from a different angle. Rather than attempting to answer these questions, the project of the positivists was to decide whether or not the questions could be answered. Here, briefly, is how they set about it.

Forget about what you can see. Think instead about what you can say.

The human vocal apparatus make it possible for you to generate all sorts of noises. Most noises are just that – noises – but some are words. Most combinations of words are nonsense: “Mill food only here bushes pardon speak and.” However, some combinations are full sentences, like “I am wearing shoes” or “The sky is green”.

The important point is that almost everything you could possibly say is actually nonsense. The things that actually mean anything – sentences – are a tiny minority. What is it about these particular utterances that makes them important? Well, sentences have a structure. They obey rules. They are not self-contradictory, like the sentence “X is and is not Y”, which is meaningless and indistinguishable from noise.

In fact, there are only two kinds of sentences that are worth talking about: sentences describing the world, and sentences describing other sentences. Any other kind of sentence is uninteresting, because hearing them does not increase one’s knowledge of the world. It’s just noise.

Now, how do we know which sentences describe the world? That’s easy: these are the sentences that can be checked against what we observe around us. “The sky is green” is an attempt to describe the world, and it is well-phrased, logical, and verifiable. It just happens to be false, because it does not match observations that show the sky is blue. The sentence “I am wearing shoes” is true (at the moment).

If you know all the meaningful, true sentences about the world, and all the meaningful, true sentences about other sentences, you will know everything that it is possible to know about the universe. Obviously, in our lifetimes we will never have this perfect knowledge. There are some things that we will never know. However, adopting this stance gives us a tool for cutting away the layers of nonsense that surround us and prevent us from understanding the world.

Does god exist? If you mean, does he exist in the world, does he have an actual location and mass and velocity we could check, then the answer is – maybe. We don’t know, but we could in principle find out. But if you mean, does he exist somehow outside the world, in a place we can never experience, then there is no question here to answer, because in that case sentences containing the word “god” are meaningless. It is impossible for an atheist to disprove the existence of god, but at the same time, anybody religious who talks about god is just making noises. What happens after we die? Again, things that happen outside the “real world” are not subject to verification, anyone who talks about it is taking nonsense. Likewise the question about the world disappearing when we close our eyes: it’s not a question that can be meaningfully answered. What is truth? Good correspondence between a sentence and observation. What is good? Whatever people say is good; people argue about it, but they argue by appeal to emotion, not to logic, unless it is to show that one’s values are inconsistent.

A lot of this is not new. Hume, much earlier, said that a book that didn’t talk about things observed or calculated should be cast onto the flames because there was nothing in it worth reading. But what the logical positivists added was the system of formal logic developed by Russell and Wittgenstein. For lovers of clarity and precision of writing, the appeal is still strong.



As always, I am not a philosopher, and could easily be getting aspects of this wrong. If so, I would be delighted to be set right by someone who knows more about it than me.

A J Ayer’s book was Language, Truth and Logic. The reference to Hume comes from his Enquiry.

Written by The S I

April 1, 2012 at 2:34 pm

Things That Don’t Look Like Anything

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When I talk about things like molecules, atoms and particles with nonscientists, a question I am often asked is what these things look like. And they never seem satisfied with my response: that, really, they don’t look like anything at all. It’s not that they’re invisible as such; it’s just that sentences involving what they look like don’t make any sense. You can’t describe their appearance because they don’t have an appearance to describe.

The thought makes people uncomfortable.

The idea of something not looking like anything is not a new one. Sounds do not look like anything. We know that sounds exist, but that physical appearance is not something we can ascribe to them. When we talk about sounds, we describe them in nonvisual terms.

Sounds, or ideas or desires or smells, have a certain abstract quality that seems to excuse this. But particles are stuff. They are physical objects whose masses are known to remarkable degrees of accuracy, and since everything we can see is made up of aggregates of them, it seems impossible that they cannot be described visually.

Let’s consider what happens when you see something, step by step.

An object is illuminated by a bombardment of photons. These photons interact with the surface of the object. Some are absorbed by the object – it is this absorption that gives the object its colour. The photons that are not absorbed are scattered around in all directions, and many of them enter through the pupil of your eye. These photons reach the retina, where they cause chemical changes in molecules like 11-cis-retinal; electrical reports of these changes are transmitted to the brain, where they are interpreted as ‘seeing’ those photons.

So to ‘see’ something means that photons bouncing off the thing cause chemical changes in your eye. This is fine for large objects like apples and oranges, but what if the object is smaller? Most people can’t see objects smaller than 0.1 mm, because there aren’t enough photons reflecting off them to react with our eyes. We get around this problem by using stronger illumination and magnifying lenses, allowing us to see things like blood cells.

But what about objects that are even smaller?

Well, here we start to have a problem. For objects smaller than 0.002 mm, photons of visible light start to be too big to see things clearly. In order to resolve details at this size level, smaller, higher-energy particles than photons need to be used. This is how electron microscopy works: instead of using reflected photons, you use reflected electrons, which are much smaller and better able to probe the surface of what you’re examining.

Is this really ‘seeing’ the object? The microscopic object under examination is not being studied with light, remember. This is why electron microscope images are monochrome. Light isn’t involved in the process at any point until a computer screen shows you, with light, the pattern of reflected electrons. Still, we are presented with pictures of the object’s surface, so it’s certainly like seeing, and the object certainly has an appearance that can be discovered, even if only indirectly.

What if the object is smaller?

Eventually an object can be so small that not even electrons can give you good enough resolution, and even more indirect means of gathering information must be used. One of them, atomic force microscopy, is more analogous to touch than sight: it drags a tiny needle across a surface to register bumps in the surface where the individual atoms are. But apart from the atoms’ location in space, there’s no information here about their appearance. Atoms do not interact with light in a way that gives meaning to the word ‘looks like’. They do absorb light and so might be said to have colour in a technical sense, but no picture of an atom could ever be drawn based on their interaction with light. And smaller particles than atoms don’t interact with light at all. You can’t see them, ever, because there is nothing there to see.

But still, some picture of a very tiny object might be drawn. Questions about its shape, for example, are not meaningless – but on a small enough scale, questions of shape become questions about properties rather than appearance. The question ‘is x round?’ becomes ‘are all the points on x’s surface the same distance from one central point?’. This is a question that can be answered, but only because it is a mathematical question about the properties of a certain type of object. And it turns out that the equations describing these objects reveal the them to be strange and wonderful things – things that behave in ways that make absolutely no sense to people used to objects the size of apples and oranges. They cannot be seen, but they can be described, and this description is better than seeing them. A mathematical description of a particle is more precise and less fallible than the clumsy tool of vision that evolution gave us to survive in a world full of large-scale objects. And we can reach this level of acquaintance with these particles that no one has ever seen because even though we can’t see them, we can imagine them.

Written by The S I

March 26, 2012 at 3:00 am

Hume on Neutrinos

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With the scientific world abuzz with reports of neutrinos appearing to travel faster than the speed of light, I have become painfully aware that what I know about modern physics I could fold in half and fit between the keys of a typewriter without seriously impeding its function.

So when I heard about the discovery, I went to what I felt to be the most relevant academic treatise on the subject, which I found highly appropriate despite it being 263 years out of date.

David Hume’s Enquiry Concerning Human Understanding was published in 1748 and deals with the problem of how we are able to know things. Since Hume believed that everything we know comes from experience ­– from evidence and experimentation, as opposed to revelation and belief – the book hits at the very core of scientific way of thinking.

When I heard of a discovery that appears to completely contradict the present scientific consensus, I went to Hume. In particular I went to chapter 10 of his Enquiry, a two-part essay entitled Of Miracles.

A miracle, for Hume, is “a violation of the laws of nature”. We determine the laws of nature by our experiences of how the world works. What we call a ‘good’ law of nature is one that we see demonstrated over and over again. Every time we have let go of a ball in mid-air, it has fallen; through habit of association we come to expect that the ball will always fall, and we arrive at a law of nature that says that all released balls fall ­– let’s call this gravity.

The questions is: how should we react to someone’s story that once he saw a ball float in mid-air ­– that he saw the force of gravity disappear? In essence, how should we react to a miracle?

Hume’s general principle, and it’s a good one, is this: “That no testimony is sufficient to establish a miracle, unless the testimony be of such a kind, that its falsehood would be more miraculous, than the fact, which it endeavours to establish.”

In the case of our friend saying the ball didn’t fall, we must ask ourselves: what is more likely? That the man is mistaken/lying/joking, or that gravity really did stop for him? If it’s just one man’s account, unsupported by evidence, then of course we are within our rights to dismiss him out of hand (A more modern commentator: “What can be asserted without evidence can also be dismissed without evidence.”)

But if he comes back with photos, confirmatory experiments, and other, independent witnesses, eventually it comes to the point where it really would be more miraculous that this was a mistake. Then gravity would be a weakened hypothesis. We would pose a new law of nature: that gravity usually holds, but in some cases doesn’t, as in the following examples…

Whatever new theory, or extension of the old one, takes the place of the traditional concept of gravity, we would listen to it, but with caution and scepticism, until the evidence in its favour built up to make it more certain.

Whenever a scientist ­– or indeed anyone at all – comes out with something new, something really new, think of sceptical old Hume. In his own words:

A wise man … proceeds with more caution: he weighs the opposite experiments: he considers which side is supported by the greater number of experiments: to that side he inclines, with doubt and hesitation; and when at last he fixes his judgement, the evidence exceeds not what we properly call probability.


Hume’s Enquiry can be found here.

Written by The S I

September 28, 2011 at 11:59 pm

You Just Think You Are

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We’re big fans of Daniel C Dennett here at the S I. This magnificently bearded Tufts philosopher has spent much of his career trying to solve the ancient puzzle of what the mind is, and how it relates to the brain. His slogan: “Yes, we have a soul, but it’s made up of lots of tiny robots.”

How is it, he asks in his book Consciousness Explained, that a collection of unthinking nerve cells can somehow go to make up a thinking, feeling being? No single brain cell knows or cares who you are. So how can the ensemble be different? What is the magic step that turns robotic components into a human whole? To try to make sense of this emergence of the self, he introduces the idea of the centre of narrative gravity.

In physics, gravity is potentially a tricky business. Consider a football. Drop a football, and any physicist will tell you it will fall. How do they know this?

It is theoretically possible to go back to first principles: calculate the gravitational attraction between all atoms in the ball and on Earth, work out the details of their interactions, then, millisecond by millisecond, determine that every atom in the ball will ultimately move downwards. But of course this is not what they do. There is a much easier way: give the football a centre of gravity. This is a single, imaginary point that stands for the whole ball. It averages out the incredible complexity of the atoms in the ball, and allows physicists to treat it as a unified entity.

Note that the centre of gravity is fictitious. Although it is located at the centre of the ball, it is not associated with an atom at the centre, or indeed any one atom. A football’s centre of gravity exists only in the minds of people who study footballs.

In the brain, Dennett argues, we have something similar. There are billions of brain cells, all firing all the time, each one telling its own story. Every time a cell fires, a set of conditions is reported – information about what a retinal cell is saying, or what the balance organs of the inner ear are saying, or what other brain cells are saying to each other. To run an efficient organism, these narratives have to be made sense of – and quickly, before the sabre-toothed tiger mentioned by one brain cell has a chance to eat you. The neurons can’t be addressed individually. Wouldn’t it be better to treat them as one thing? This is where the self comes in.

Who are you? You are your brain’s centre of narrative gravity: you are the point in space around which the experiences reported by your brain cells cluster. You, unified, singular you, are a fiction generated by your brain, as flag to rally defences around.

It is your brain cells, working together, that are reading these words right now. You, the person, are not. You just think you are.

Written by The S I

July 14, 2011 at 8:25 pm

Posted in Science

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