The Standing Invitation

Posts Tagged ‘Hume

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.

 

REFERENCES

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.

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Written by The S I

April 1, 2012 at 2:34 pm

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.

REFERENCES

Hume’s Enquiry can be found here.

Written by The S I

September 28, 2011 at 11:59 pm