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At the workshop Langton began with his quest for a definition of
life. Existing ones seemed inadequate. As more research was started over
the years following the first conference, physicist Doyne Farmer proposed
a list of traits that defined life. Life, he said, has:
- Patterns in space and time
- Self-reproduction
- Information storage of its self-representation (genes)
- Metabolism, to keep the pattern persisting
- Functional interactions -- it does stuff
- Interdependence of parts, or the ability to die
- Stability under perturbations
- Ability to evolve.
The list provokes. For although we do not consider computer viruses
alive, computer viruses satisfy most of the qualifications above. They are
a pattern that reproduce; they include a copy of their own representation;
they capture computer metabolistic (CPU) cycles; they can die; and they
can evolve. We could say that computer viruses are the first examples of
emergent artificial life.
On the other hand, we all know of a few things whose aliveness we don't
doubt yet are exceptions to this list. A mule can not self-reproduce, and
a herpes virus has no metabolism. Langton's success in creating a
self-reproducing entity made him skeptical of arriving at a consensus:
"Every time we succeed in synthetically satisfying the definition of life,
the definition is lengthened or changed. For instance if we take Gerald
Joyce's definition of life -- a self-sustaining chemical system capable of
undergoing Darwinian evolution -- I believe that by the year 2000 one lab
somewhere in the world will make a system satisfying this definition. But
then biologists will merely redefine life."
 Langton had better luck defining
artificial life. Artificial life, or "a-life" in short hand, is, he said,
"the attempt to abstract the logic of life in different material forms."
His thesis was that life is a process -- a behavior that is not bound to a
specific material manifestation. What counts about life is not the stuff
it is made of, but what it does. Life is a verb not a noun. Farmer's list
of qualifications for life represent actions and behaviors. It is not hard
for computer scientists to think of the list of life's qualities as
varieties of processing. Steen Rasmussen, a colleague of Langton who was
also interested in artificial life, once dropped a pencil onto the desk
and sighed, "In the West we think a pencil is more real than its motion."
If the pencil's motion is the essence -- the real part -- then
"artificial" is a deceptive word. At the first Artificial Life Conference,
when Craig Reynolds showed how he was able to use three simple rules to
get dozens of computer-animated birds to flock in the computer
autonomously, everyone could see that the flocking was real. Here were
artificial birds really flocking. Langton summarized the lesson: "The most
important thing to remember about a-life is that the part that is
artificial is not the life, but the materials. Real things happen. We
observe real phenomena. It is real life in an artificial medium."
Biology -- the study of life's general principles -- is undergoing an
upheaval. Langton says biology faces "the fundamental obstacle that it is
impossible to derive general principles from single examples." Since we
have only a single collective example of life on Earth, it is pointless to
try to distinguish its essential and universal properties from those
incidental properties due to life's common descent on the planet. For
instance, how much of what we think life is, is due to its being based on
carbon chains? We can't know without at least a second example of life not
based on carbon chains. To derive general principles and theories of life
-- that is, to identify properties that would be shared by any vivisystem
or any life -- Langton argues that "we need an ensemble of instances to
generalize over. Since it is quite unlikely that alien life-forms will
present themselves to us for study in the near future, our only option is
to try to create alternative life-forms ourselves." This is Langton's
mission -- to create an alternative life, or maybe even several
alternative "lifes," as a basis for a true biology, a true logic of Bios.
Since these other lifes are artifacts of humans rather than nature, we
call them artificial life; but they are as real as we are.
The nature of this ambitious challenge initially sets the science of
artificial life apart from the science of biology. Biology seeks to
understand the living by taking it apart and reducing it to it pieces.
Artificial life, on the other hand, has nothing to dissect, so it can only
make progress by putting the living together and assembling it from
pieces. Rather than analyze life, synthesize it. For this reason, Langton
says, "Artificial life amounts to the practice of synthetic biology."
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