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in answer to the question of whether

an agent can still “think for himself”

after indoctrination. And what is it

to be able to think for ourselves? We

must be capable of being “moved by

reasons”; that is, we must be reasonable

and accessible to rational persuasion,

the introduction of new evidence, and

further considerations. If we are more

or less impervious to experiences that

ought to influence us, our capacity has

been diminished.

The only evidence that HAL might be

in such a partially disabled state is the

much-remarked-upon fact that he has

actually made a mistake, even though

the series 9000 computer is supposedly

utterly invulnerable to error. This

is, to my mind, the weakest point in

Clarke’s narrative. The suggestion that

a computer could be both a heuristically

programmed algorithmic computer

and “by any practical definition of the

words, foolproof and incapable of error”

verges on self-contradiction. The whole

point of heuristic programming is that

it defies the problem of combinatorial




mathematically solve by sheer increase

in computing speed and size—by taking

risky chances, truncating its searches

in ways that must leave it open to error,

however low the probability. The saving

clause, “by any practical definition of the

words,” restores sanity. HALmay indeed

be ultra-reliable without being literally

foolproof, a fact whose importance

Alan Turing pointed out in 1946, at the

dawn of the computer age, thereby

“prefuting” Roger Penrose’s 1989

criticisms of artificial intelligence.**

(See my

Darwin’s Dangerous Idea

, chapter

15, for the details.)

The Monolith

**The verb prefute, coined in 1990,

was inspired by the endearing

tendencyof psichologist TonyMarcel

to interrupt conference talks by

leaping to this feet and exclaiming,

“I can see where your argument is

heading and here is what is wrong

with what you’re going to say”

Marcel is the master of prefutation,

but he is not its only practitioner.