aac423 at agora.ulaval.ca
Sun Apr 13 16:29:27 EST 1997
Interview with Lotfi Zadeh, Creator of Fuzzy Logic
by Betty Blair
Lotfi Zadeh was born in Baku, Soviet Azerbaijan, in 1921; today,
his scientific concept, Fuzzy Logic, has strongly impacted
computer technology, tomorrow it may be shaping the way we
perceive the world.
Q: Back in 1965 when you published your initial paper on Fuzzy
Logic, how did you think it would be accepted?
Well, I knew it was going to be important. That much I knew. In
fact, I had thought about sealing it in a dated envelope with my
predictions and then opening it 20-30 years later to see if my
intuitions were right. I realized this paper marked a new
direction. I used to think about it this way-that one day Fuzzy
Logic would turn out to be one of the most important things to
come out of our Electrical Engineering Computer Systems Division
at Berkeley. I never dreamed it would become a worldwide
phenomenon. My expectations were much more modest.
Q: How did you think Fuzzy Logic would be used at first?
In many, many fields. I expected people in the social
sciences-economics, psychology, philosophy, linguistics,
politics, sociology, religion and numerous other areas to pick up
on it. It's been somewhat of a mystery to me why even to this
day, so few social scientists have discovered how useful it could
be. Instead, Fuzzy Logic was first embraced by engineers and used
in industrial process controls and in "smart" consumer products
such as hand-held camcorders that cancel out jittering and
microwaves that cook your food perfectly at the touch of a single
button. I didn't expect it to play out this way back in 1965.
Q: How did you come up with the term, "Fuzzy Logic"?
I coined the word "fuzzy" because I felt it most accurately
described what was going on in the theory. I could have chosen
another term that would have been more "respectable" with less
pejorative connotations. I had thought about "soft", but that
really didn't describe accurately what I had in mind. Nor did
"unsharp", "blurred", or "elastic". In the end, I couldn't think
of anything more accurate so I settled on "fuzzy".
Q: Would you say that Fuzzy Logic turns Aristotelian or Classical
Logic on its head?
(Laughs). Back in Aristotle's day, people tried to be as precise
as possible. That's the Aristotelian tradition, the Cartesian
tradition. Looking at things as being entirely black or white
stems from such a tradition. But take the example of good and
bad. What we're beginning to understand now is that sometimes
things that we perceive as bad really turn out to be good, or
perhaps not as bad as we originally thought. Things can serve a
purpose. People back in Aristotle's time and even later thought
that by perceiving things in black and white (in absolute terms)
that they gained alot. And they did. But they lost a great deal
in the process. Fuzzy Logic represents a swing in the opposite
direction but I would like to stress that there is much more to
Fuzzy Logic than multi-valuedness of truth.
Classical logic has erred in devoting so little attention to
approximate reasoning and focusing to such a high degree on exact
reasoning. So when you take a course in logic, you learn all
kinds of things which are of very little use in everyday life. We
encounter approximate reasoning all the time. For example, "Where
can I park my car?" Where should I have lunch? Should I place
this call "person-to person" or "station to station"? Should I
buy this house? How do I get from this side of town to the other
when I'm in a hurry? Classical logic, operation research,
decision analysis- many other disciplines have nothing to say
about this topic.
Q: How could they ignore it?
When the only tool you have is a hammer, everything begins to
look like a nail. Classical logic simply doesn't provide the
means to solve the problems. They concerned themselves with
models of precise knowledge. But such models are so far removed
from the real world that they don't do you any good.
There's a field called "Game Theory." Hundreds of books and
thousands and thousands of articles have been written about it
since the late 40s. Now you might think that by reading those
books and articles and by taking courses, you would be in a
better position to play games of various kinds. But the truth is,
it doesn't do you a bit of good. Not one iota. Game Theory is
concerned with models that are not tied to real games and only
tenuously tied to real world conflicts.
Q: Why are you so "down to earth" in your own approach to solving
I'm that kind of person. I've been conscious for a very long time
that the real world is very complex. There's always a tendency to
oversimplify. That was the case in physics. In my youth, we had
very simple models. About electrons in orbit. About protons.
Models of the solar system. Of course, today we realize that
these were ridiculous. The physics of these phenomena are
infinitely more complex.
Today we do the same with neuro-systems. We think that there is a
close similarity between those systems and what goes on in our
heads. But that's not the case. There's a big gap. There are big
gaps in many fields.
Q: Why is Fuzzy Logic described as "cheaper" and "easier" than
traditional methods of computing?
Fuzzy Logic is "coarse". The important thing about Fuzzy Logic is
that it's done in a "coarse" way- not refined. Anything that is
coarse-grained is simpler and cheaper. If, for example, you want
to park a car and somebody said, you had to do it within (+/-)
1/10 of an inch of some particular point, you'd be in trouble.
The reason why people can do things like park a car is that they
don't have to be very specific to succeed.
Many people don't realize that this is one of the very important
features of Fuzzy Logic. You use what I call "granulation" which
means you lump things together. It makes things easier, cheaper
and faster. If you had a bunch of screws and nuts and you picked
up one screw at a time and took it some place and then came back
for another, it would take a long time. Dump them together in a
bag and it's faster. That's what you do with Fuzzy Logic.
Q: Everybody is talking about the Japanese being so advanced in
Fuzzy Logic. Is that true?
It's true. The Japanese are very consumer oriented. They are
incorporating Fuzzy Logic into many of their products, especially
appliances and electronic equipment. But I just returned from
Germany a few days ago (October 21st) and was very impressed by
what is happening there. There are many, many people working on
Fuzzy Logic both in industry and the universities. There are many
good papers and books. I would say that next to Japan, Germany is
the country with the highest level of activity.
Q: And where would you place the United States?
Third. Russia used to be high up there and there used to be quite
a few scientists interested in Fuzzy Logic and a number in
Azerbaijan. But with the breakup of the Soviet Union, there's no
money for these things now.
Q: China is very active, too, isn't it?
The Chinese Government used to be very supportive of Fuzzy Logic.
Scholars there have written quite a few papers related to
traditional Chinese medicine, mathematics and engineering. You
often hear a figure of 10,000 Chinese scientists involved with
Fuzzy Logic. That figure refers to the activity before the events
of Tiennenman Square. The government used to support Fuzzy Logic
in a big way back then, but now some of the most active people
have left for Singapore and Hong Kong. They've scattered. I guess
the Chinese government didn't like that so many of the leaders of
that movement turned out to be Pro-Western and as some sort of
punishment, they've decreased the funding for Fuzzy Logic, not to
zero but much lower than it was before. I haven't been to China
to see what's happening since 1985. My understanding is that
support is beginning to pick up again and is likely to grow
Q: There seems to be a close correlation between Fuzzy Logic and
Linguistics. So much of what is inherent in Fuzzy Logic relates
to the way people think and talk- in other words, their use of
natural language. What influence did your early exposure to so
many different languages play in shaping these attitudes?
(Before Zadeh was twelve, he was having to deal with four
different languages- Russian, Azerbaijani, Persian, and
English- and three separate scripts- Cyrillic, Arabic, and
You're right. The Fuzzy Logic model relates closely to
linguistics. But I'm not sure learning these languages had a big
influence on my thinking. If it did, then only subconsciously.
But I do remember one thing that made a very deep impression on
me in my youth. That was how different people could
wholeheartedly embrace systems- whether political, religious,
social, whatever- that were diametrically opposite.
After leaving Azerbaijan as a child, I attended Alborz College, a
Presbyterian missionary school in Tehran. Every morning, we had
to go to chapel- that was a drastic change from what I had
experienced at the Soviet atheistic schools. But from this
experience, I grew to be tolerant of many different points of
view- Soviet atheism, Protestantism, and Muslim fundamentalism.
At the same time, I'd have to admit that I did gain something
from early exposure to all these cultures. It's clear now as I
look back. For example, the Soviets placed science and technology
on a very high pedestal. They also instilled the belief that you
owed something to society. That you shouldn't be self-centered,
egoistic, seeking only your own pleasure. That you should focus
on what contribution you could make to others.
In Iran, I was deeply influenced by the decency of these American
missionaries who ran the school which I attended. It's the sort
of decency that one finds in the US if you go to the Midwest or
rural areas- away from the big cities. To me, these people were
role models- so willing to help others who were not of the same
ethnic origin. They weren't nationalistic. They had a mission and
they stuck to it. That influenced me deeply.
Then while studying at the University of Tehran, the intellectual
climate at that time was deeply influenced by the French culture
as most of the professors had been educated in France along the
lines of Cartesian tradition. That means they were very precise.
So even though you might be thinking about very imprecise things,
you had to think about them very precisely. Fuzzy Logic is like
that. It's really an exact way of thinking about very ambiguous
and obscure things. (Zadeh pulls an issue of the International
Journal of Fuzzy Sets and Systems from his shelves and thumbs
through the pages.) You see, pages and pages of very precise
mathematical formulas. Fuzzy Logic is not abstract thinking. In
reality, it's very concrete. It's built on very precise formulas.
Also from Iran, I learned a certain kind of warmth. People are
warm in that part of the world. There's a great depth to their
friendships. People tended to be polite. Looking back, I feel it
was a very positive experience for me to have grown up in Iran.
There's a great respect for knowledge there. Even if an
individual didn't have anything by way of material goods, he was
highly respected if he were knowledgeable.
Q: And what about the influence from Azerbaijanis?
Obstinacy and tenacity. Not being afraid to get embroiled in
controversy. That's very much a Turkish tradition. That's part of
my character too. I can be very stubborn. That's probably been
beneficial for the development of Fuzzy Logic.
Q: And Russia? Your mother was Russian, wasn't she?
>From the Russians I gained a great respect for knowledge- a broad
based knowledge. I read so many books as a child- Dostoyevsky,
Chekhov, Tolstoy. Those books put goodness on a pedestal. The
heroes of those books were always fighting evil. You'll find the
pursuit of goodness on all their pages, except for Dostoyevsky. I
had a library of, maybe, 3,000 books since my father had been a
journalist. I read Shakespeare in Russian. There was such a
respect for knowledge in my youth.
There was another factor that deeply influenced my early life,
too. I grew up as an only child. I remember I used to have a sign
over my desk that read, "Alone" (in Russian). I was alone much of
the time and that enabled me never to feel pressure to be like
others or do what others did. I never felt I had to go along with
the crowd. I've always felt separated enough so I could go my
individual way. It's always been that way.
Q: You must be quite pleased to see how the field of Fuzzy Logic
has expanded so much in these past 25 years, especially since
the late 1980s.
I don't feel any different now than I did 15-20 years ago.
Somedays, I'm pleased with the progress; sometimes not. C'est la
vie! But basically, I don't have an egocentric view of myself. I
never felt that I was an important person. I feel ordinary like
anybody else. I have no feeling of importance. No such feeling
whatsoever. I don't attach very much importance to who I am.
Q: Looking back on the development of Fuzzy Logic and its
application, what would you have done differently to promote
I've made no effort to go after scientists or companies to show
them how my theories could be applicable to their work. I don't
promote this thing. If people want to do something, that's fine.
If they don't, that's fine, too.
Q: What kinds of applications have you been excited to
I can't say that anything has been "exciting". Rather, I would
choose the word "interesting". Not too long ago, the Chinese
University of Hong Kong conducted a survey to determine which
consumer products were using Fuzzy Logic. The result was a thick
report, some 150-200 pages long- washing machines, camcorders,
microwave ovens, etc. What interested me wasn't the particular
applications so much as the breadth of applications- so many
products were incorporating Fuzzy Logic.
Q: What would be the ultimate application of Fuzzy Logic?
I can't say that I have much time to think much about such things
because I have to focus on more immediate deadlines- like this
speech I'm giving in New York to a Semantics group on November
4th (one week from now). I tend to think about things closer to
the present. I have to do quite a bit of thinking about those
things; if I didn't, I'd soon sound like a broken record and they
wouldn't invite me to these conferences. I always feel like I
have to say something different than what I've said before.
Q: What's the future for Fuzzy Logic?
In general, I think the future will involve fuzzy logic, neural
networks and genetic algorithms. I lump all these under the
rubric of "soft computing". I'd encourage people who have the
inclination and ability to become competent in all three of these
areas. Eventually, I believe that Fuzzy Logic will have a
wide-ranging impact once it is understood how widely the theory
can be applied. Of course, this is just my opinion; only time
What is Fuzzy Logic?
Fuzzy Logic is not what it sounds like. It's not a nebulous,
cloudy, vague way of thinking; in fact, it's quite the opposite.
When anything becomes too complex to fully understand, then it
becomes uncertain. The more complex something is, the more
inexact or "fuzzier" it will be. Fuzzy Logic provides a very
precise approach for dealing with uncertainty which grows out of
the complexity of human behavior.
The concept was first articulated by Lotfi Zadeh in a paper
published in 1965, ("Fuzzy Sets," Information and Control 8:3,
338-53) which provided the theoretical basis for fuzzy computer
chips which appeared 20 years later.
Unlike traditional or classical logic, which attempts to
categorize information into binary patterns such as black/white,
true/false, yes/no, or all/nothing, Fuzzy Logic pays attention to
the "excluded middle" and tries to account for the "grays", the
partially true and partially false situations which make up 99.9%
of human reasoning in everyday life. It builds upon the
assumption that everything consists of degrees on a sliding
scale- whether it be truth, age, beauty, wealth, color, race, or
anything else that is effected by the dynamic nature of human
behavior and perception. The question Zadeh always insists upon
asking is, "To what degree is something true or false?"
Zadeh looks around him in the real world which he finds pervaded
by concepts which do not have sharply defined boundaries, where
information is often incomplete or sometimes unreliable. In fact,
he would classify most words as having fuzzy meanings- virtually
every adjective or adverb in ordinary speech. These concepts
become clear if seen in transition from membership to
non-membership in gradual, rather than abrupt, increments.
In quest for precision, scientists have generally attempted to
manipulate the real world into artificial mathematical models
that make no provision for gradation. They have tried to describe
the laws governing the incredibly complex behavior of humans,
both singly and in groups, in mathematical terms similar to those
employed in the analysis of inanimate systems, which, in Zadeh's
view, has been, and will continue to be, a misdirected effort.
Because the human mind can't handle so many isolated separate
ideas at one time, it tends to bundle similarly-related objects
into categories in such a way as to reduce the complexity of the
information processing task. It is this incredible capacity of
the human mind to manipulate these fuzzy or unsharp categories
that distinguishes human intelligence from the machine
intelligence of current generation computers.
Because Fuzzy Logic provides the tools to classify information
into broad, coarse categorizations or groupings, it has infinite
possibilities for application which have proven to be much
cheaper, simpler and more effective than other systems in
handling complex information. Fuzzy Logic has extremely broad
implications for many fields not just electrical engineering and
computer technology which have been fairly quick to incorporate
its theoretical principles. Numerous consumer goods especially
household products and electronic equipment- microwaves, cameras,
and camcorders already incorporate Fuzzy Logic into their design.
So have computer control systems such as the famous subway of
Sendai, Japan, or numerous complex diagnostic and monitoring
biomedical systems which are starting to be used in hospitals.
But other fields such as the social sciences- economy, finance,
psychology, sociology, politics, religion, ethics, law, medicine,
geography, folklore, anthropology that deal with the complexity
of human behavior- are just beginning to explore the infinite
possibilities of Fuzzy Logic.
Zadeh was not the first to think about "shades of gray".
Philosophers such as Plato indicated that there was a third
region (beyond "true" and "false") where opposites "tumbled
about". Hegel, Marx, Engels and Lukasiewicz, among others, also
dealt with middle regions. But it was Zadeh who first developed
the general theory and laid the foundation for what Fuzzy Logic
For a well-researched, very readable, popular description of
Lotfi Zadeh and the development of the field of Fuzzy Logic,
refer to Daniel McNeill and Paul Freiberger's award winning book,
Fuzzy Logic: The Revolutionary Computer Technology that is
Changing our World, 1993. For a technical introduction to the
field, see Zadeh's Fuzzy Sets and Applications: Selected Papers.
Edited by Yager, Ovchnikov, Tong, and Nguyen. New York: Wiley,
Lotfi Zadeh: A Short Biographical Sketch
He was born in 1921 in Baku, Soviet Azerbaijan; but in truth, as
creator of the concept of "Fuzzy Logic", Lotfi Zadeh belongs to a
world where there are no boundaries limited to time or place. He
really is best characterized as an internationalist. He's quick
to shrug off nationalism, insisting there are much deeper issues
in life. "The question really isn't whether I'm American,
Russian, Iranian, Azerbaijani, or anything else," he'll tell you.
"I've been shaped by all these people and cultures and I feel
quite comfortable among all of them."
It's a vivid example of how in real life Zadeh shuns abrupt
absolute categories that don't take into account life's
complexities. It's the same kind of thinking that characterizes
Fuzzy Logic, an unorthodox theory which he invented which is
impacting computer technology.
Born of an Azerbaijani father on assignment as a journalist from
Iran, and a Russian mother who was a physician, Zadeh enjoyed a
privileged life those early years of his life in Baku. But at the
age of ten, when Stalin introduced collectivization of farms
throughout the Soviet Union, widespread famine followed, and the
Zadeh family moved back to his father's homeland. There he
continued his education in English in a private Presbyterian
school in Tehran. After high school, he sat for the national
university exams and placed second in the entire country. In
1942, he graduated from the University of Tehran in electrical
During World War II, he moved to the US and took a Master's
degree from Massachusetts Institute of Technology (MIT) in 1946
and a Ph.D. from Columbia (New York) in 1949, where he began
teaching systems theory. Since 1959, Zadeh has taught at
Berkeley, first in the Electrical Engineering (EE) Department
where he became Chair in 1963, and later in the Computer Science
Retirement? Since 1991, he's been officially "retired" though
it's hard to imagine how he could keep a busier schedule. He
still continues to go to his office on campus everyday when in
town; but conferences and consultations, often abroad, keep him
away, on average, a few days each week. He generally takes the
"red-eye" flights to the East Coast, preferring to travel all
night because his schedule is too tight to spend much time
hanging around in airports and hotels.
Lotfi Zadeh, in person, is a lean, quiet, unpretentious,
unassuming sort of man. He's often described as extremely
gracious- a "gentleman" in the European sense of the word- even
by those who don't agree with him. He's methodical, given to
details, a "pencil person" (preferring the eraser's tentativeness
over pen). During his leisure, he's extremely fond of photography
though he used to have more time for it in years past than now.
Black and white portraiture (with its fine nuances of grays, of
course) is his favorite. He has photographed quite a few famous
people himself, including Presidents Truman and Nixon.
His original paper on Fuzzy Logic published in 1965 encountered
skepticism and, in his words, occasional, downright hostility.
Nearly thirty years later, the controversy surrounding Fuzzy
Logic is still with us, though not to the same extent. The
numerous applications of Fuzzy, especially in Japan, are too
visible to be denied.
He's gifted with a mind that provides the flexibility to address
learned scientists as well as the most unindoctrinated novice by
describing scientific principles in concrete tangible examples
from everyday life. He tries to best to be accessible to both
Although Fuzzy logic has a much longer reach than traditional
logical systems, Zadeh is the first to admit that it is not a
panacea. "There are and will be many tasks which humans can
perform with ease and which lie beyond the capability of any
computer, any machine and any logical system that we can conceive
How Big is "Fuzzy"? Who knows? Zadeh is too busy pushing forward
to keep up with how far the field has expanded. His office in the
newly constructed Computer Science Building at Berkeley is
stacked floor to ceiling with reprints of articles related to
Fuzzy. He believes that people are studying this field in every
country which offers advanced education. Twelve journals are now
published which include the word "Fuzzy" in their title. An
estimated 15,000 articles have been published, although it's hard
to be exact as some appear in obscure journals in remote parts of
the world. An estimated 3,000 patents have been applied for and
1,000 granted. The Japanese, with 2,000 scientists involved in
Fuzzy Logic, have been very quick to incorporate Fuzzy Logic in
the design of consumer products, such as household appliances and
electronic equipment and one company, Mitsushita (which sells
under the name of Panasonic and Quasar) acknowledged that in
1991-1992 alone, they had sold more than 1 billion dollars worth
of equipment that used Fuzzy Logic. The concept is so popular
there that the English word has entered the Japanese language,
though the Japanese pronounce it more like "fudgy" than "fuzzy".
Zadeh's intellectual contributions are myriad. He's listed in
"Who's Who in the World" and since the late 1980s when the
Japanese became interested, the field has expanded exponentially.
So, too have the acknowledgments of these contributions with
honors such as the esteemed Honda Prize in Japan in 1991, medals,
honorary memberships, doctorates, fellowships, editorships, and
chairmanships from all over the world. Azerbaijan Republic is
among those who have honored him in 1993 when they bestowed an
honorary Professorship from the Azerbaijan State Oil Academy.
Characteristically, Zadeh is "down-to-earth", always holding
abstract scientific concepts up to a reality check of their
practical utility of whether they "do us any good." Since the
applications of Fuzzy Logic to real life situations are infinite;
it's extremely likely that we'll be hearing about Zadeh for a
long, long time to come.
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