Excuse me! Could I have a minute of your time, please?

When the average human uses numbers, he gets vague and fuzzy, and it doesn't matter
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Very Unusual Jobs Indeed

No 44 in our series

A professor of domestic mathematics

Stephen Hope-Bastable is professor of domestic mathematics at Milton Keynes University. But what is domestic maths? Is it really different from any other kind of maths? And where on earth did a new kind of maths come from when we weren't looking?

"Oh, come on !" says the ebullient Professor Hope-Bastable. "The public is always ready for another kind of maths. Ten years ago nobody had heard of `chaos theory', and now they accept it. They haven't the faintest idea what it is, but they accept it. I hope they will do the same for domestic maths."

And what is domestic maths when it is at home?

"It is a recognition that imprecision has its own value," says Professor Hope-Bastable, warming to his subject. "It is a recognition of the fact that when the average human uses numbers, he gets vague and fuzzy, and that it doesn't matter. For instance, when we say to a friend that we will see them in `a minute', we don't actually mean a minute, do we? We don't literally mean in 60 seconds. It could mean five minutes or 10 minutes. It almost never is a minute. But it is almost always obvious from the context what is meant, and the other person usually knows.

"Same in cookery, when we say `a pinch of salt' or `a knob of butter'. Same with the word `couple'. Couple means, literally, two. But when we say that we'll be down in `a couple of minutes', or that I've got to go to the shops to get `a couple of things', we never mean, literally, two. Could be anything up to half a dozen.

"And it gets better than that. Sometimes we say `in a couple of ticks' or `in a couple of shakes', where `couple' doesn't mean `couple' and `ticks' and `shakes' don't mean anything at all. Yet we always know exactly what is meant, don't we?"

Does that mean that vagueness has its own integrity?

"And I'll tell you another thing," says Professor Hope-Bastable, ignoring the question with all the enthusiasm of a teacher used to addressing a captive audience, "domestic maths reveals that we very often ask the wrong question, and therefore get the wrong answer. For instance, if you were getting some washing out of the tumble dryer, and found you had, not a pair of light blue socks but three light blue socks, what would be your first thought?"

I'd probably think: "Where did that third sock come from?"

"Exactly! But what you should ask, of course, is: `Where did the fourth blue sock disappear to?' You see? Same facts; different question. Makes all the difference. Here's another one: how many balloons do you tie on your gatepost to signify you're having a party? Half a dozen? Ten? Twelve? More?

"You see, you don't know, do you? Actually, all you can say with certainty is that it should be more than one - because one balloon tied to a gatepost is just sad - and less than 100, because 100 balloons would look silly. But what is the correct number? There is no correct number! Only a vaguely correct number. It's like asking: `How many sections are there in a newspaper?'"

Right. So, how many sections are there in a newspaper?

"Only one. Whatever the editor may think, a newspaper is a newspaper and doesn't have sections. Only bits that fall out."

What about the business section? Isn't that a section?

"Well, occasionally the business pages are printed separately, but that doesn't make them a separate section. What about a newspaper that has its business news in the body of the paper? The business coverage may be just as good, even though it's not a section. And which bit of the Financial Times is the business section? No, you can't really subdivide a paper into sections, any more than you can divide the year into seasons."

But we do divide the year into seasons!

"Yes. Odd, isn't it? Who says that there are four seasons in a year? Two I could understand. The cold bit and the hot bit. The wet bit and the dry bit. But four? Why do we give a separate seasonal name to the transitional periods? In some cultures, autumn is just the end of summer, and not a separate season at all. You see..."

Let's leave the professor there. Let's tiptoe out of the room and leave him talking. Because, according to domestic maths, if I've got this right, the talker and the listener can sometimes be the same person. And in this instance it seems better that way.