The Semantic Web, Syllogism, and Worldview - Clay Shirky
Skip to content
Customize -> Theme Options) -->
Search for:
Archives
November 2013
November 2012
December 2010
November 2010
April 2010
March 2009
February 2009
April 2005
May 2004
March 2004
December 2003
November 2003
October 2003
September 2003
July 2003
June 2003
May 2003
March 2003
February 2003
January 2003
November 2002
October 2002
September 2002
June 2002
May 2002
April 2002
June 2001
May 2001
April 2001
March 2001
February 2001
January 2001
December 2000
November 2000
October 2000
September 2000
July 2000
June 2000
May 2000
April 2000
February 2000
January 2000
December 1999
November 1999
October 1999
September 1999
August 1999
July 1999
June 1999
April 1999
March 1999
February 1999
October 1998
April 1998
March 1998
January 1998
November 1997
April 1997
October 1996
March 1996
December 1994
Meta
Log in
The Semantic Web overestimates the value of deductive logic, and underestimates the difficulty of shared worldview.
Essays
Popular
Leave a comment
First published November 7, 2003 on the "Networks, Economics, and Culture" mailing list.
The W3C’s Semantic Web project has been described in many ways over the last few years: an extension of the current web in which information is given well-defined meaning, a place where machines can analyze all the data on the Web, even a Web in which machine reasoning will be ubiquitous and devastatingly powerful. The problem with descriptions this general, however, is that they don’t answer the obvious question: What is the Semantic Web good for?
The simple answer is this: The Semantic Web is a machine for creating syllogisms. A syllogism is a form of logic, first described by Aristotle, where "…certain things being stated, something other than what is stated follows of necessity from their being so." [Organon]
The canonical syllogism is:
Humans are mortal<br>Greeks are human<br>Therefore, Greeks are mortal
with the third statement derived from the previous two.
The Semantic Web is made up of assertions, e.g. "The creator of shirky.com is Clay Shirky." Given the two statements
– Clay Shirky is the creator of shirky.com<br>– The creator of shirky.com lives in Brooklyn
you can conclude that I live in Brooklyn, something you couldn’t know from either statement on its own. From there, other expressions that include Clay Shirky, shirky.com, or Brooklyn can be further coupled.
The Semantic Web specifies ways of exposing these kinds of assertions on the Web, so that third parties can combine them to discover things that are true but not specified directly. This is the promise of the Semantic Web — it will improve all the areas of your life where you currently use syllogisms.
Which is to say, almost nowhere.Syllogisms are Not Very Useful #
Though the syllogism has been around since Aristotle, it reached its apotheosis in the 19th century, in the work of Charles Dodgson (better known as Lewis Carroll.) Dodgson wrote two books of syllogisms and methods for representing them in graphic form, and his syllogisms often took the form of sorites, where the conclusion from one pair of linked assertions becomes a new assertion to be linked to others.
One of Dodgson’s sorites goes:
– Remedies for bleeding, which fail to check it, are a mockery<br>– Tincture of Calendula is not to be despised<br>– Remedies, which will check the bleeding when you cut your finger, are useful<br>– All mock remedies for bleeding are despicable
which lets you conclude that Tincture of Calendula will check the bleeding when you cut your finger.
Despite their appealing simplicity, syllogisms don’t work well in the real world, because most of the data we use is not amenable to such effortless recombination. As a result, the Semantic Web will not be very useful either.
The people working on the Semantic Web greatly overestimate the value of deductive reasoning (a persistent theme in Artificial Intelligence projects generally.) The great popularizer of this error was Arthur Conan Doyle, whose Sherlock Holmes stories have done more damage to people’s understanding of human intelligence than anyone other than Rene Descartes. Doyle has convinced generations of readers that what seriously smart people do when they think is to arrive at inevitable conclusions by linking antecedent facts. As Holmes famously put it "when you have eliminated the impossible, whatever remains, however improbable, must be the truth."
This sentiment is attractive precisely because it describes a world simpler than our own. In the real world, we are usually operating with partial, inconclusive or context-sensitive information. When we have to make a decision based on this information, we guess, extrapolate, intuit, we do what we did last time, we do what we think our friends would do or what Jesus or Joan Jett would have done, we do all of those things and more, but we almost never use actual deductive logic.
As...