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Mark Leech on causality and coffee.
“Why is it so hard to make a cup of coffee?”
It had not been a good night in the Empirical Eatery. Sir Isaac Newton, a guest of some importance it had to be said, had chosen to come on the new chef’s first night. The encounter had not been a pleasant one. Everything had been undercooked, and in one case - the chicken that had run off into the night - not cooked at all. George Berkeley, supporting his philosophical earnings with a spot of part time waiting on, had been worried since the first course when he had seen the cold vegetables arranged on the plate in the pattern of billiard balls. “Oh no,” he had muttered. “He’s having a sceptical turn.” He stood next to the indignant scientist’s table wearing his most patient smile. “I’m sorry, Sir Isaac. It’s the new chef-”
“What’s wrong with him?”
“Causation, Sir Isaac. He has a problem with the coffee machine…”
In the kitchen David Hume scratched the back of his head and stared irritably at the percolator. It was charged with coffee and filled with water. Only the ‘on’ button needed to be pressed. But that was the problem. “All you need to do is switch it on.”
“Maybe, but I don’t see why doing that would make it work. Look, we’re all empiricists here. We need to have evidence that we can observe before we can know anything. That’s the basis of our whole philosophy. But we haven’t got any evidence that if I press that button the coffee will be made.”
“What does he mean? It’s always done it before! It’ll do it again! Why wouldn’t it?” Newton’s wig practically leaped off his head and his fingers pulled at his lacy shirt cuffs. Berkeley smiled and raised his eyes to heaven. But Sir Isaac wasn’t finished yet. “The evidence is all there in front of us!” He flapped his napkin, showering the philosophical bishop with crumbs. “Look. Empirical science draws on evidence, experimental evidence. We observe the results of our experiments and from them we draw laws.” He looked round him with a satisfied smile. “I’m, erm, something of an expert on the matter. Anyway, these laws. The basic idea is that if you put a given thing in a given set of circumstances it will always act in the same way. This breadstick, for example.” He waved it under Berkeley’s nose. “If I bash it on the edge of the table it’ll break into two big bits and lots of little ones.” He did this. “See? But imagine if that was the first time that anyone had done that. They might wonder what would happen next time. So they’d do it again to find out.”
Berkeley wiped more crumbs off his clothes. “Yes. Yes I see,” he said without enthusiasm.
“And after repeated experiments they’d conclude that every time you bash a bit of breadstick on the table edge it would break in a similar way: Stick + table edge = bits of stick. If you tried with a soggy breadstick though -” Berkeley quickly moved the water jug out of reach. “- you’d get different results and have to have a different law governing soggy breadsticks. That’s evidence, see? And by using the evidence to get laws about events you can build up a picture of the way the world works. So therefore if Mr Hume just presses the button the percolator will follow the laws of coffee. He will cause the coffee to be made according to physical laws, drawn from experimental evidence, which apply at all times to physical objects in similar circumstances.”
Newton coughed slightly and smiled up at Berkeley, who sighed. “So you want me to tell him that the interaction of physical objects is predictable with reference to predetermined laws. And the subjection of those objects to those laws is a sufficient explanation of causation, so he needn’t worry?”
“That’s about right. Show him this.” Newton scribbled on the napkin with a pencil he had pulled from a pocket. “The rate of change of momentum of a moving body is proportional to the force acting to produce the change. So make him hurry up.”
David Hume wiped his forehead. “You’ve got pencil on your face now,” Berkeley said, pointing to the smudged writing.
“Well it’s rubbish anyway. I don’t know. You lob fruit at a guy and he thinks he’s the father of modern science.”
“Yeah, but he is.”
“Oh shut up. The point is that he’s saying that he knows that if I turn the coffee machine on it will make coffee because such an act would be in accordance with physical laws based on previous experimental evidence. The problem is that, as an empiricist, a proper empiricist that is, if I was going to make a law I would require proper evidence. I’ve got no evidence that this time when I press the button the same thing will happen as what’s happened before. Laws are all very well -” he brandished the napkin. “But they’re based on assumptions, not evidence. If I carry out all my experiments here which demonstrate that coffee is made, or that breadsticks break, in a certain way, any laws I make based on that evidence really only relate to that evidence. I can assume that coffee and breadsticks will behave like that all over the universe if the conditions are right, but I haven’t experimented with them on the moon, or in the future. So I can’t say for certain that what applies here would necessarily apply there or then because the laws I have made here are not based on evidence drawn from the other places. I can’t know that pressing ‘on’ on the coffee machine in the future will cause coffee to be made. Custom and habit make us expect that event B will follow event A because event B has always followed event A before. But an empiricist confronted with the complete lack of any real experimental evidence from the future of this coffee machine might wonder if perhaps event B, the coffee, is not really a necessary consequence of event A, the pressing of the switch. Perhaps event C might follow in spite of the fact that event B has always happened before. The coffee might grow wings, or get cold instead. I’m not saying that something like that will happen, or even that it’s likely, but there’s no empirical guarantee that it won’t, no matter how many laws you quote.”
“So what do you want me to tell him?”
“Give him his napkin back and refer him to the phrase of mine that everybody quotes.”
“What, the one about your first book ‘falling dead-born from the press’?”
“No, no. I meant the question ‘From what impression is that supposed idea derived?’ You know, impressions being direct experience and the ideas being the thoughts derived from that experience. If he’s a proper empiricist he’ll agree with me that all valuable ideas derive directly from a given impression, and that any idea that can’t be traced to an impression is a bit silly. Newton’s so-called universal laws are only based on a small amount of evidence. They’re valid for that evidence, but their universality is really only an idea. Therefore they’re a bit silly. I can’t turn the coffee machine on because I don’t know what’ll happen if I do.” “Right. I’m sure that’ll make him happy.”
It didn’t. Sir Isaac was not amused and threatened to call the manager. Berkeley, knowing who the manager was, had to think quickly. Seizing the breadstick jar and waving it extravagantly in the air he began to talk at the top of the startled scientist’s head. “I think I see a way out of the problem.” He crunched the end of a stick. It was Newton’s turn to be on the end of a gentle powdery shower. “I don’t know though. Maybe you’re too much of a Deist.”
“Look here, I want my coffee.”
“Fair enough. The way I see it, the problem is that you see phenomena as the product of inanimate objects blindly acting according to unchanging laws, while Hume doesn’t see any guarantees existing beyond what’s already been observed. Basically, neither of you see the universe as anything other than collections of phenomena with God pretty much taking it easy even if he can be bothered to exist at all.”
“That’s a bit of an over-simplification…”
“If we’re going to get into that argument I’m going home. But listen, think of how the picture changes if you let God get his hands on things. I’m an empiricist like everyone else, and I agree that all our knowledge about the world comes ultimately from our perceptions of it – evidence, like you’ve both been wittering on about. The problem is that if an object is not perceived we’ve got no evidence about it.” Sir Isaac shifted uneasily in his chair. He was beginning to regret ordering the coffee. Berkeley didn’t notice, and he swung the jar of breadsticks with even more enthusiasm. “Which implies that if an object is not perceived and therefore we know nothing about it,it might as well not exist – it doesn’t exist. I would say it doesn’t, not physically anyway. Everything we know comes from our perceptions. What we don’t perceive doesn’t, practically, exist. Which means that the world, effectively and literally, exists within our perceptions. Therefore, in a way, we make the world. We don’t merely observe it the way he and you think we do.”
“Phew!” said Sir Isaac. “If I get my coffee after this it’ll be a miracle.”
“Exactly!” Berkeley shouted. “Listen – when we look at what we perceive we see a kind of evidence that points to only one end. Everyone – to some degree – encounters the same evidence. Both of us, if we break a breadstick, feel showers of crumbs.” He demonstrated. Newton, who was breathing heavily, sneezed. “It’s pretty amazing that if the physical world only exists within our perceptions we both feel the same things. It’s also pretty amazing that if we both drink some of Hume’s coffee, if he ever gets round to making it, we experience something completely different from the snapping breadstick, yet also something consistent with our own experience, and – ” He drew a deep breath. “something that we both agree has certain characteristics. If everything simply depended on our own perceptions which, as I’m sure you’ll agree, are limited, there’d be something that didn’t match up, surely. I reckon though that the consistency and the range of our perception gives evidence that something else perceives our universe.”
“Right. God then?”
“Yep. If God perceives everything then, as far as we’re concerned, everything exists. Whatever he perceives, we are also capable of perceiving. He is the source of all perception. I’m not going to say that things exist as such, physically, but if God perceives them we can perceive them. His perception is our guarantee that what we perceive is true.” Sir Isaac made a muttering noise, as though he wanted to speak, but Berkeley carried on relentlessly. “I know I sound a bit like Descartes – he was in here last week, only had two courses. Dualists, I don’t know. But I’m not a dualist. The physical world only exists in the sense that it is sensed by God and us. And if God is the guarantor of objects then it doesn’t take much to see that he’s also the guarantor of interactions between those objects. He’s the direct cause of the interactions that result in the coffee being made.
“Hm. You don’t seem very impressed. But I don’t see why my argument’s any more ridiculous than either you saying that laws based on a few experiments are applicable everywhere, or Hume saying that he’s worried about the future of a coffee machine. Please stop banging your head on the table. You’ll upset the other guests.”
After closing time Hume and Berkeley were enjoying a quiet drink. Both had double whiskies. It had been a long day after all. “So he didn’t want his coffee after all then?” asked Hume.
“No. He wasn’t too keen on the whole God thing. He was even less keen when he got the bill. He said ‘it didn’t relate to what he’d ordered’, and asked for the manager.”
“Ouch. What happened?”
“Well, the usual. Mr Einstein came over, stuck his tongue out at him and said ‘That’s relativity for ya’. Complete chaos.”
© Mark Leech 2000
Mark Leech lives in London.