Monday, January 31, 2011

The Swimming Submarine

"The question of whether a computer can think is no more interesting than the question of whether a submarine can swim." - Edsger Dijkstra
One can imagine a long, heated and intricate debate among fish philosophers (in schools of philosophy), on the question of whether it could ever be possible for a submarine to truly swim. While some animals (for example humans and jellyfish) can achieve a certain amount of propulsion through water, fish-philosophers have long believed that only a fish can move with the power, speed and agility underwater that constitutes true swimming. However, recent engineering advances in Artificial Swimming (AS) have produced devices that have extraordinary swimming power by some measures. Some of them can even outpace fish over longer distances. Most fish-philosophers, however, are dismissive of AS. They say:

"Why, these 'submarines' aren't swimming! They don't even have proper beating tails! They are just hunks of metal with tiny revolving tails and minuscule fins at the back! They don't swim like we swim."

Swimming competitions are held. The submarines win. The fish-philosophers simply laugh and say:

"Ok, so you can beat us at swimming in a straight line, but what about swimming together in a shoal while being chased by a predator?"

As advances in AS encroach further into the definition of swimming that fish-philosophers hold; new, tougher, tests are introduced, such as the Tuna test, in which a submarine has to convince a fish, while swimming alongside it, that it is actually another fish. After a half century of work in AS, simple, cheap, readily available submarines can defeat a fish in almost every test of swimming that was traditionally used in swimming competitions between fish; yet still, fish philosophers refuse to accept that a submarine really has that ephemeral, fishy-swimming quality that makes the way fish swim distinct from how machines swim. Some fish philosophers even maintain that it would be possible for an organism to exist that was physically identical to a fish, behaved just like a fish, moved through the water exactly like a fish, but was still incapable of true swimming. This idea had previously only been suggested in low-budget fish horror movies.

One can imagine endless debates among birds about featherism. Elephants using artificial trunks. Arachnid science-fiction writers concerned that spider-engineers will construct web-spinning machines so advanced that they turn against their creators and catch all their flies. When a skill is considered to be the defining characteristic of a species, attempts to artificially engineer a machine to emulate this skill will be considered an affront to the very existence of the species. So it is with humans and thought.

This hubris must end. Machines think. Machines learn. Machines are intelligent. There does not exist a computer that thinks exactly as I do, but in terms of the ability to "think", as that word has been used historically, modern computer systems think better than modern humans. In this blog, I want to highlight pieces of AI and Machine Learning research that provide evidence of Machine Intelligence that is often ignored in other communities, mainly because Computer Science and Psychology/Philosophy don't always communicate very well. Occasionally I will also try to make a joke. Sorry about that.

My attitude to the philosophical debates on strong AI is summed up by the Dijkstra quotation. If you're interested in his views on computing he written on his "personal perspective":
Selected Writings on Computing: A Personal Perspective


  1. Polar bears use their front paws to swim, not their hind legs.

  2. Brilliant. I love the references to the concept of philosophical zombie, it really shows how absurd that concept is.

    Although I think the statement that "modern computer systems think better than modern humans" is a hard one to swallow. (likewise, I don't think that modern airplanes fly "better" than birds, even though they certainly do fly, and in some ways they do it better)