- The limits to computing are not the limits
of physical device.
They're not the limits of concrete or steel
or anything like that in the physical world,
the limits to computing are the limits of your imagination.
When the first computers began to appear
in the late 1940s, early 1950s,
people were fascinated by these incredibly complex machines
that could do things like process huge numbers
of mathematical equations incredibly quickly.
And so there was a buzz at the time
around these electronic brains.
Lots of people thinking around
could machines really be intelligent?
So Alan Turing, I think, was one
of the most remarkable people in the 20th century.
What he did was he invented a beautiful test.
He said, "Look, here is this test.
If we ever get something that would passes it,
then just stop asking that question
because you can't tell the difference."
He never really expected that anybody was seriously going
to try it out, but actually people did try it out.
But it's been wildly misinterpreted, I say since then.
What Turing's most famous for is working at Bletchley Park,
a code breaking center in the United Kingdom
throughout the Second World War.
And actually, if that was the only thing he'd done
in his life, he would have a place in the history books.
But almost as a side product of his PhD work,
he invented computers, which are just any one of
the most remarkable sort of, you know, quirks of history.
And with incredible precociousness,
he picked one of the biggest mathematical problems
of the age, the Entscheidungsproblem,
which means decision problem;
whether mathematics can be reduced to following a recipe.
So the question that Turing asked was, is it the case
that for any mathematical problem that you might come up
with, you can find a recipe which you can just follow
in the same way that you would follow for arithmetic?
Incredibly quickly, within about 18 months,
Turing solved it.
And the answer is no,
mathematics doesn't reduce to following a recipe.
But the interesting thing is what Turing did
is to solve that problem, he had to invent a machine
which could follow instructions,
and nowadays we call them Turing machines,
but actually it's basically a modern computer.
And he was one of the first serious thinkers about AI.
And so in 1950, he published what we think
is the first real scientific work
around artificial intelligence.
If we ever achieved the ultimate dream of AI,
which I call the Hollywood dream of AI,
the kind of thing that we see in Hollywood movies,
then we will have created machines
that are conscious potentially in the same way
that human beings are.
So Alan Turing, I think, was really frustrated
by people saying, "Well, no, of course these machines can't
be intelligent or creative or think or reason," and so on.
So Turing's genius was he invented a beautiful test.
We call it the Turing Test in his honor.
Okay, so here's how the test goes.
You've got somebody like me,
who's sitting at a computer terminal with a keyboard
and a screen, and I'm allowed to ask questions.
I type out questions on the keyboard,
but I don't know what's on the other end, right?
I don't know whether it's a computer program
or another human being.
So Turing's genius was this.
He said, "Well, look, imagine after a reasonable amount
of time, you just can't tell whether it's a person
or a machine on the other end.
If a machine can fool you into not being able
to tell that it's a machine,
then stop arguing about whether it's really intelligent
because it's doing something indistinguishable.
You can't tell the difference.
So you may as well accept that it's doing something
which is intelligent."
And I think Turing never really expected
that people would seriously try it out.
And so there are annual Turing Test competitions
across the world where people will enter computer programs,
and there will be judges who will try
and tell whether they're a computer program
or a human being.
Most of the entries in them are like these kind
of crude internet chat bots.
And what these chat bots do is they just look for keywords
like sad or family or lonely or drunk
or something like that.
And they plug that keyword into a canned response.
And so they're really just trying to fool the investigators.
And I have to say- there's not really much AI
in most of those programs because they're doing something
which is really much more superficial.
It's a boom period for AI now because a very narrow class
of techniques have turned out to be very successful
on a wide range of problems.
Modern AI is really focused on doing very specific tasks,
and in those specific tasks like playing a game of chess
or something, it might be better
than any living human being,
but it can't do anything else.
Those programs are just tuned, very finely tuned,
to do one tiny thing very well.
But going back to Alan Turing's invention,
he invented machines that for following lists
of instructions, but the computer
can adapt those instructions.
It can learn to adapt those instructions over time.
And that's basically what you're doing in machine learning.
He's one of the founders of the field,
not just of computing, but also of artificial intelligence.
One of the most remarkable people of the 20th century.