Now for some remarks on TT.
My What Robots Can and Can't Be [6] is a sustained, rigorous case for the two-part view that
P-BUILD, i.e., it's logically impossible
that computationalists build persons.Most of this case is devoted to demonstrating the first of these two propositions. The part of it concerned with substantiating the second is, as I readily admit in the monograph in question, inchoate. A forthcoming book of mine, Literary Creativity, Story Generation, and Artificial Intelligence [2], is devoted in earnest to bolstering TT-BUILD. This book features a storytelling agent, BRUTUS, able to (among other things) ``understand" and manipulate the concept of betrayal.
Actually, TT-BUILD is short for a thesis that makes crucial reference
not only to the
Turing Test ( 
) but to
what has been called [6] the Turing Test sequence.
There are obviously
tests easier to pass than , but which
still capture Turing's empiricism.
For example, we might index to some
particular domain -- golf, say -- and stipulate that questions moving
significantly beyond
this domain aren't fair game.
We might insist that the syntax of queries,
and the syntax of responses, conform to a certain range of patterns.
Or we might decide to modify the scoring that is part of Turing's original
proposal -- so that, for example, if a system can fool the judge 25% of time,
rather than the full 50%,
it is judged to have passed.
It's also easy enough to devise tests more stringent than .
The most famous of these tests is Stevan Harnad's [13]
intriguing ``Total
Turing Test," which we can baptize as 
. In this test not
only is the linguistic behavior of a robot
(or android) scrutinized, but its sensorimotor conduct
is evaluated as well. In order
to pass , a robot must not only have the capacity to be
an articulate (to use one of
Harnad's terms) pen-pal; it must also look human.
In the same paper, Harnad
considers more stringent tests than , for example tests in which
the judge is allowed to ``look under the hood," that is, to look at the
physical stuff out of which the synthetic contestant is made.
Other thinkers, for example Peter Kugel [14], have proposed
tests so demanding that they cannot,
as a matter of mathematics, be passed by Turing Machines.
And so on. Let's suppose,
accordingly, that there is indeed some sequence
which underlies the relevant modification of TT-BUILD, namely,
I think TT-BUILD is true, and I hope to provide
increasingly powerful evidence for this proposition as the years unfold.
But I think a claim of the form `if x passes
then x is conscious,' that is, TT 
,
is false. I have two types of arguments
for this position; each is based on a series of thought-experiments.
The first series begins with a gedankenexperiment
in which an excruciatingly simple LISP-based
random sentence generator
serendipitously passes . Would we want to say, in such a situation,
that as luck would literally have it, a new consciousness has popped
into existence? I would think not. After all, such a sentence generator
is easy enough for a novice in AI to write -- an observation that
underlies this argument:
This argument is specified and defended in [5], and
is then extended in that same paper
so as to refute TT 
and beyond.
The extension allowing for the refutation of TT , i.e., a refutation
of
is easily produced: the trick is to combine the random sentence generator (from above) with a random ``behavior" generator, i.e., a program that randomly outputs not only text, but also commands to effectors. Now imagine that this composite computer program, when hooked to some real effectors, serendipitously passes Harnad's Total Turing Test. Would anyone want to say that the system in question is conscious? I doubt it. But then it follows that the conditional in question has been overthrown, since it's antecedent is true while its consequent isn't.
Of course, I'm assuming that the conditional in TT is
stronger than a material conditional, for
if this conditional is of this type,
then since no machine can currently pass the test ( = TT)
in question,
the thesis is (vacuously) true. What Turing had in mind was
no doubt something a bit stronger -- probably something
like
(I consider this modal version of thesis, and a number of other possibilities, in [5].) On the assumption that this sort of stronger thesis is what's at issue, I move directly to the fact that Harnad has produced a more sophisticated thesis to accompany his Total Turing Test, one he specified near the end of a long debate between the two of us, viz.,
-H
Unfortunately, this thesis is false -- given that Harnad
accepts (a modalized interpretation of the conditional, which he does, and)
my argument from serendipity (and Searle's
Chinese Room Argument [20] against the original
Turing Test). In order to
see this, begin by supposing that x is TTT-indistinguishable
(TT -indistinguishable)
from someone with a mind. To make this a bit more vivid, suppose that
roboticist Smith escorts a robot around with him which is
TTT-indistinguishable from someone with a mind, but suppose
that Smith cloaks this robot in some way (with synthetic skin
that passes for the real thing, artificial eyes that look human,
etc. -- use your imagination) and refers to it as `Willie.' So,
you carry out conversations with Willie for years; and,
since we're dealing here with the Total Turing Test, you also
play
baseball (and the like) with Willie for years. And then one day
Smith says, ``Aha! Watch this!" And he tears off the skin over
Willie's forehead, and therein sits a computer busy humming along.
So far so good. How do we get the falsity of TT -H's consequent built
into the thought-experiment? No problem. Let's begin
by reminding ourselves of what we need. We need the Willie scenario
to include the falsity of
Let's instantiate this to me; that seems harmless enough. So we need the scenario to include the falsity of
Here's how it works:
Selmer says to Smith: ``Look, Willie is still just a
bunch of symbols swimming around inside a box. There's no person in the
picture. It's easy enough to show that there's no principled connection
between the symbols and sensors/effectors working nice and there being a
person in the picture, for consider a situation
(alluded to above) wherein Willie's program
is a composite program: a lucky random sentence generator and a
lucky program for processing information received via sensors and a
lucky program for processing information sent to effectors -- all code
that's based on technology students master in the first few weeks of
Intro to AI."
(It's important to note here that (i) all I need to overthrow Harnad's
TT -H
is a non-arbitrary reason for denying that Willie is conscious;
I don't need a compelling reason. And (ii) Harnad
agrees that TT 
is shown to be false by the original version of
the argument from serendipity.)
In the second
type of attack on the Turing Test, I argue that zombies, contra
Dennett, are logically -- and, in fact, physically -- possible,
and that this fact suffices to refute certain versions of
computationalism.
The initial thought-experiment in the series of them that underlies this
attack is provided by Searle in his
The Rediscovery of the Mind.
I move now to a brief look at the rest of my theory of mind.