The complexities of the mind mirror the challenges of Artificial Intelligence. This article discusses the nature of thought itself–can it be replicated in a machine? From Ray Kurzweil's revolutionary book The Age of Intelligent Machines, published in 1990. At a time when computer technology is advancing at a breakneck pace and when software developers are glibly hawking their wares as having artificial intelligence, the inevitable question has begun to take on a certain urgency: Can a computer think? In one form or another this is actually a very old question, dating back to such philosophers as Plato, Aristotle, and Descartes. And after nearly 3,000 years the most honest answer is still "Who knows?" After all, what does it mean to think? So let's try some others.

This is an updated version of Usability Issues in Description Logic Systems'' published in Proceedings of International Workshop on Description Logics, Gif sur Yvette, (Paris), France, September, 1997.

In 1955 the computer scientist John McCarthy, who has died aged 84, coined the term artificial intelligence, or AI. His pioneering work in AI – which he defined as "the science and engineering of making intelligent machines" – included organising the first Dartmouth conference on artificial intelligence, and developing the programming language Lisp in 1958. This was the second high-level language, after Fortran, and was based on the radical idea of computing using symbolic expressions rather than numbers. It helped spawn a whole AI industry. McCarthy was also the first to propose a time-sharing model of computing.

Born in the vicarage in Lenham, Kent, he was the second of the parish priest's three children. He joined The Pilgrim's school, Winchester, in 1932 and became a senior chorister at the cathedral. Three years later, he won the top entrance scholarship to Winchester College, where his precocious talents in mathematics and music flourished. In 1941, he won a scholarship to Balliol College, Oxford, to read chemistry, but at the end of his first year also took part one of the music tripos, and was appointed Balliol organ scholar. In his second year, Christopher performed what Dr John Jones has described as "probably the greatest intellectual feat by a Balliol undergraduate ever": he proposed, with convincing arguments, the correct structure of the chemical compound diborane (B2H6) - a compound that defied contemporary chemical valency principles.

Originating as a BBC radio series in 1978, Douglas Adams's inspired melding of hippy-trail guidebook and sci-fi comedy turned its novelisations into a publishing phenomenon. Douglas wrote five parts from 1979 onwards (the first sold 250,000 in three months), introducing the world to Marvin the Paranoid Android, the computer Deep Thought, space guitarist Hotblack Desiato (named after Adams's local estate agent) and the Guide itself, a remarkably prescient forerunner to the internet. Aldiss's first novel is a tour-de-force of adventure, wonder and conceptual breakthrough. Set aboard a vast generation starship millennia after blast-off, the novel follows Roy Complain on a voyage of discovery from ignorance of his surroundings to some understanding of his small place in the universe. Complain is spiteful and small-minded but grows in humanity as his trek through the ship brings him into contact with giant humans, mutated rats and, ultimately, a wondrous view of space beyond the ship. One of the first attempts to write a comprehensive "future history", the trilogy - which also includes Foundation and Empire (1952) and Second Foundation (1953) - is Asimov's version of Gibbon's Decline and Fall of the Roman Empire, set on a galactic scale. Hari Seldon invents the science of psychohistory with which to combat the fall into barbarianism of the Human Empire, and sets up the Foundation to foster art, science and technology.

Babylonians develop the clepsydra, a clock that measures time using the flow of water. It's considered one of the first "robotic" devices in history. For centuries, inventors will refine the design. Around 270 BC, the Greek inventor Ctesibius becomes famous for a water clock with moving figures on it. The Greek philosopher Aristotle imagines the great utility of robots, writing, "If every tool, when ordered, or even of its own accord, could do the work that befits it then there would be no need either of apprentices for the master workers or of slaves for the lords."

MUNICH, Germany Computer pioneer and philosopher Joseph Weizenbaum (85) has died in Berlin. The scientist and MIT professor emeritus was known for his critical position towards the impact of information technology to society. Born in Berlin to Jewish parents, Weizenbaum had emigrated in 1936 to the United States. After having contributed to the development of the first analog computers and participating in the design of the first digital computers for banking applications, Weizenbaum in 1963 took a position at the Massachussetts Institute of Technology (MIT); from 1970 he was professor for computer science. Among his major achievements were studies over the SLIP programming language and research on basic software technologies which today are in widespread use such as garbage collection algorithms.

WHO would have thought that a Frisbee-shaped contraption that extracts dust from carpets would be the state of the art in household robots at the dawn of the 21st century? In the past year, Roomba, a circular automatic vacuum cleaner made by a firm called iRobot, has swept up millions of dollars from over 200,000 buyers--and was a must-have at Christmas, among geeks at least. Rival firms such as Electrolux and Karcher sell similar but pricier sweepers. Robot vacuum cleaners, it seems, are catching on. Are these mere playthings, or the beginning of a new trend?

IN 1981 Kenji Urada, a 37-year-old Japanese factory worker, climbed over a safety fence at a Kawasaki plant to carry out some maintenance work on a robot. In his haste, he failed to switch the robot off properly. Unable to sense him, the robot's powerful hydraulic arm kept on working and accidentally pushed the engineer into a grinding machine. His death made Urada the first recorded victim to die at the hands of a robot. This gruesome industrial accident would not have happened in a world in which robot behaviour was governed by the Three Laws of Robotics drawn up by Isaac Asimov, a science-fiction writer.

Christos Papadimitriou, the C. Lester Hogan Professor of Electrical Engineering and Computer Science at the University of California at Berkeley, is this year's recipient of the Katyanagi Prize for Research Excellence. Carnegie Mellon University has cited Dr. Papadimitriou as "an internationally recognized expert on the theory of algorithms and complexity, and its applications to databases, optimization, artificial intelligence, networks and game theory." We recently spoke with Papadimitriou, where among other topics we delved into the underpinnings of science, the economics of the programming market, the mysterious complexity of the Web, quantum computing, and the computer scientist as popular novelist. Next month, we talk with Dr. Erik Demaine, recipient of this year's Katyanagi Emerging Leadership Prize. CP: I didn't know I had been nominated. She mentioned the previous winner, so I thought someone else won the prize and that I was invited to speak at the ceremony. I replied, "Yeah, okay, let me think about it, give me a week..." She wrote back in astonishment, thinking I was not accepting the prize!