Re: Request for information from a complete non-fuzzy person

Martin Sewell (martin@msewell.force9.co.uk)
Mon, 26 Oct 1998 02:49:07 +0100 (MET)

Hi

Isn't it odd that the most innocuous posting can cause some threads to just
run and run?

If you subscribe to the belief that anything can be justified if it's funny
enough, well, who can criticise Earl's first posting? Admittedly it was
post-pub viewing - but it's not often that I laugh out loud when sharing the
room with no one else besides a PC.

Michael was criticized for not spending any time actually researching the
ideas behind fuzzy logic - or even trying to learn the basic principles.
But surely the point is that this is precisely what he was doing by posting
to the group! The FAQ for the group is not always available (I've never
seen it). People may wish to get a taste for all things fuzzy before
deciding whether to spend some money on a book.

Any book, almost by definition will have a built in bias because the author
writes about his/her interest - which then becomes a source of interest to
others, which then becomes a source of income. Of course one should use all
resources available to form their own views, which includes buying books on
fuzzy logic. The point really is that, for instance, I haven't seen many
books on astrology written by a sceptic. Astrology, of course is utter
nonsense (I take it we can all agree on this one guys!).

Incidentally, out of all those replies Michael got - I noticed that no one
really did try to explain how the Tokyo subway braking system actually
works! It's surely in your interest to avoid a closed shop approach and
treat newcomers and nonbelievers with help and constructive argument
respectively. Okay, humour's appreciated too!

So what do I think of fuzzy logic? Well, I wanted to use it as part of an
Intelligent Trading System, but now I have my suspicions. So here goes . .
.

Fuzzy logic is nothing more than a reformulation of statistical inference
and probability theory. This does not of course, in itself, make it any
less useful. For instance, computing is just a mixture of electricity and
logic. What does bother me though is that there is no single formulation of
fuzzy logic, based on some simple axioms. Unlike set theory and
probability.

(As an aside, there are in fact some paradoxes in set theory. For example,
Russell's Paradox (or the Barber's Paradox): Let Z be the set of all sets
which do not contain themselves as members. Question: Does Z belong to
itself. When this problem was discovered it completely screwed up the whole
of set theory! - until a work around could be found.)

In fuzzy theory, none of the existing formulations correctly handle compound
propositions in which the parts are not independent. For example, some
fuzzy logic statements concerning (A and not A) appear spurious to me.

It could be argued that set theory/probability is a limiting special case of
fuzzy logic. It could also be argued that probability exists 'inside' fuzzy
theory, which appears to contradict the first statement.

But . . . are there real-world situations where fuzzy theory is beneficial?
What about the case where you need to unify information obtained from
numerical and text data and the numerical data needs to be fuzzified? Or
perhaps it is useful for minimizing the number of equations, or dealing with
missing or inconsistent data? Still sounds like a free lunch to me.

Sorry, I forgot these postings are best kept short and sweet. I'm now off
to hide somewhere in the GA or nonlinear groups!

Regards

Martin Sewell
martin@msewell.force9.co.uk

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