IMMATERIAL BOY:

Chains of cause and effect seem to be everywhere. Stubbing my toe causes pain; clapping my hands makes a noise; poking a bear provokes it to eat me.

But Hume's analysis says otherwise. Stubbing my toe, from a Humean perspective, is a bit like lighting a cigarette at the bus stop: just as the lit cigarette only appears to make the bus arrive, so stubbing a toe only appears to cause pain.

All I can say with any certainty is that in my experience thus far, every time I've stubbed a toe it has hurt. But that doesn't determine anything necessary about the future, and it certainly doesn't stack up to an ironclad universal law.

As Helen Beebee, Professor of Philosophy at the University of Manchester, puts it: "It's certainly Hume's view that we can't prove any connection between events. There's no 'sensory impression', as Hume would put it, of causation. When you look at two billiard balls, you just see the one hitting the other and then the other one moving, you don't see any connection".

This leads Hume to the conclusion that causation, far from being one of the fundamental laws of the universe, is more a projection of the human mind.

"As far as we can know, all that's out there in the world is just one thing happening, and then another", says Professor Beebee.

"But then we have this impression of necessary connection, which we somehow impose upon reality. So in a sense, we invent the causal structure of the world".

This sort of analysis has fixed Hume in the popular imagination as an arch sceptic. But was he really?

According to the British philosopher and author Julian Baggini, we need to be careful when we apply the S-word to Hume.

"I think that even Hume scholars sometimes get him a bit wrong on this," he says.

"In some ways, yes, he was a radical sceptic. He didn't believe that by the use of reason alone, one can establish any of the most fundamental truths required for living -- in particular, the existence of cause and effect".

But this doesn't mean that Hume was the kind of sceptic who simply suspends judgement about the existence of any and every natural phenomenon.

"You still find philosophy textbooks that say 'Hume did not believe in cause and effect as a real power in nature'. And I think that's just obviously not true", says Baggini.

"What Hume doesn't believe is that by observation or by logic we can prove that causation exists. It's something that reason can't establish -- but it has to be taken as true nonetheless. Experience tells us that we're right to take it as true, even though our arguments are weak".

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