Letter to the Patent Office From Professor Donald Knuth

Letter to the Patent Office
From Professor Donald Knuth
February 1994

Commissioner of Patents and Trademarks
Box 4
Patent and Trademark Office
Washington, DC 20231

Dear Commissioner:

Along with many other computer scientists, I would like to ask you to
reconsider the current policy of giving patents for computational
processes. I find a considerable anxiety throughout the community of
practicing computer scientists that decisions by the patent courts and
the Patent and Trademark Office are making life much more difficult
for programmers.

In the period 1945-1980, it was generally believed that patent law did
not pertain to software. However, it now appears that some people
have received patents for algorithms of practical importance–e.g.,
Lempel-Ziv compression and RSA public key encryption–and are now
legally preventing other programmers from using these algorithms.

This is a serious change from the previous policy under which the
computer revolution became possible, and I fear this change will be
harmful for society. It certainly would have had a profoundly
negative effect on my own work: For example, I developed software
called TeX that is now used to produce more than 90% of all books
and journals in mathematics and physics and to produce hundreds of
thousands of technical reports in all scientific disciplines. If
software patents had been commonplace in 1980, I would not have been
able to create such a system, nor would I probably have ever thought
of doing it, nor can I imagine anyone else doing so.

I am told that the courts are trying to make a distinction between
mathematical algorithms and nonmathematical algorithms. To a computer
scientist, this makes no sense, because every algorithm is as
mathematical as anything could be. An algorithm is an abstract
concept unrelated to physical laws of the universe.

Nor is it possible to distinguish between “numerical” and
“nonnumerical” algorithms, as if numbers were somehow different from
other kinds of precise information. All data are numbers, and all
numbers are data. Mathematicians work much more with symbolic entities
than with numbers.

Therefore the idea of passing laws that say some kinds of algorithms
belong to mathematics and some do not strikes me as absurd as the 19th
century attempts of the Indiana legislature to pass a law that the
ratio of a circle’s circumference to its diameter is exactly 3, not
approximately 3.1416. It’s like the medieval church ruling that the
sun revolves about the earth. Man-made laws can be significantly
helpful but not when they contradict fundamental truths.

Congress wisely decided long ago that mathematical things cannot be
patented. Surely nobody could apply mathematics if it were necessary
to pay a license fee whenever the theorem of Pythagoras is
employed. The basic algorithmic ideas that people are now rushing to
patent are so fundamental, the result threatens to be like what would
happen if we allowed authors to have patents on individual words and
concepts. Novelists or journalists would be unable to write stories
unless their publishers had permission from the owners of the
words. Algorithms are exactly as basic to software as words are to
writers, because they are the fundamental building blocks needed to
make interesting products. What would happen if individual lawyers
could patent their methods of defense, or if Supreme Court justices
could patent their precedents?

I realize that the patent courts try their best to serve society when
they formulate patent law. The Patent Office has fulfilled this
mission admirably with respect to aspects of technology that involve
concrete laws of physics rather than abstract laws of thought. I
myself have a few patents on hardware devices. But I strongly believe
that the recent trend to patenting algorithms is of benefit only to a
very small number of attorneys and inventors, while it is seriously
harmful to the vast majority of people who want to do useful things
with computers.

When I think of the computer programs I require daily to get my own
work done, I cannot help but realize that none of them would exist
today if software patents had been prevalent in the 1960s and 1970s.
Changing the rules now will have the effect of freezing progress at
essentially its current level. If present trends continue, the only
recourse available to the majority of America’s brilliant software
developers will be to give up software or to emigrate. The
U.S.A. will soon lose its dominant position.

Please do what you can to reverse this alarming trend. There are far
better ways to protect the intellectual property rights of software
developers than to take away their right to use fundamental building

Donald E. Knuth
Professor Emeritus


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