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Kees van Deemter: The importance of being vague

Liz Else, Associate editor


Forgive the oxymoron, but how do you define vagueness?




Is vagueness anathema to science?

Put a magnifying glass to many scientific concepts and you find vagueness. Take the idea of "species". For centuries, biologists searched for crisp distinctions between species. A common definition today is to say that two animals only belong to the same species if they can interbreed. But if A can interbreed with B, and B with C, it doesn't always follow that A can interbreed with C.

Take the Ensatina salamander, which has six subspecies. Suppose subspecies A can interbreed with B, B with C, and so on until the end of the chain when F can no longer breed with A. Intuitively you want to say that they are all one species, but your criterion disagrees.

Should we give up on the concept?

The notion is incoherent, but biologists continue using it - with a pinch of salt. Richard Dawkins calls this tendency to think in discrete categories "the tyranny of the discontinuous mind".

So we think in discrete categories, but reality really isn't that way?

In the book I talk about a vintage racing car that has been repaired so many times that 70 years later only a few of the original parts remain. Is it the same car? The boundaries of objects are vague - and that goes for us, too. The average age of adult cells is 10 years. We are changing all the time.

Describing the world in terms of discrete objects is a useful fiction. Classical logic is discrete, too, based on binary dichotomies: yes/no, true/false. But that is not suited to thinking about the world's fundamentally vague things, which include some of the things science is based on, such as measurement. There is, for example, no such thing as a "perfect" metre, imperfect approximations are all we have. We should recognise we often need other forms of mathematical logic to describe the world.

How vague is everyday life?

Vagueness seeps in everywhere. We think we know what things like obesity or poverty are but they are context-based concepts. It can be a matter of life and death. We have laws prohibiting poisonous substances in food, say, but ask toxicologists what poisonous means, and all they give you is degrees of toxicity. Thresholds are arbitrary.

Is it ever important to be vague?

Doctors use vagueness all the time. For example, when researching for a project to automate messages about the condition of babies in intensive care, my colleagues found that doctors' written reports say things like: "heart rate OK most of the night, on the high side in the morning". The vagueness of the messages works in a very smart way - leaving out irrelevant details while adding a little bit of opinion. By calling the heart rate high, for example, they suggest there may be cause for worry.

For all these reasons, vagueness is crucial if you want to build computers and robots that communicate with people. If you want to understand or generate language, getting to grips with vagueness is key.

Will the web need vagueness?

As we move toward a semantic web where the formal representations are symbolic, the challenge is to figure out how to represent vague or gradable things, such as "affordable" housing or "ancient" monuments.

Check out our editorial:

We need to think precisely about vagueness

Book Information:
Not Exactly: In praise of vagueness by Kees van Deemter
Oxford University Press, $29.95

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Politicians are way ahead of you. They've embraced vagueness even where it's not warranted.


This is why I dont like powerful 32 bit CPUs in robots, being accurate to 1 part in 4 billion, they cannot handle the response time that a thousand times slower 8 bit CPU is that only has to be accurate to 1 part in 256. After all, in that time, things change. If your measuring approximately to start with, its more likely the variation is going to be within system quantisation limits at a given clock speed, even though the speed is much lower.

Try looking at a direct sampling 8 bit Z80 CPU from the 80s, at 1 Mip, then the filtering you need to add to a 500 Mhz 32 bit CPU from the present.

Now use a thousand, networked, to sense and operate your human complexity robot.

Heisenbergs Dog chases Shroedingers Cat.


Maybe a good start would be defining a proper vague number system. People use error tolerances all the time but it isn't part of a formal algebra, why shouldn't it be. Take the equation
x*x = 4, z*z = 4, y = x + z
y might be 4, it might be -4, but is most likely to be 0. So y is a vague number.


I think this approach to the concept of vagueness and why vagueness
is essential is rather crude.- you notice the succession of vaguenesses in as simple a sentence as thiese two declaration.within the associative network of the mind - that is all the mind is, a huge interconnections vagueness functions as a filter to get to the specific via various, via a mass of vaguenesses..MICHAEL ROLOFF

Member Seattle Psychoanalytic Institute and Society

This LYNX will LEAP you to my HANDKE project sites and BLOGS

"Degustibus disputandum est." Theodor Wiesenthal Adorno
"May the foggy dew bediamondize your hoosprings + the fireplug
of filiality reinsure your bunghole! {James Joyce}
"Siena me fe, disfescimi Maremma." [Dante]
experience." Walter Benjamin, the essay on Leskov.

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