Life O Screen: Situated Robotics and the Strong Claim
of Articial Life
Josh Bongard
History and Philosophy of Adaptive Systems, Spring 1999
MSc, Evolutionary and Adaptive Systems (Full Time)
School of Cognitive and Computing Sciences
University of Sussex
Professor: M. Boden
April 19, 1999
Abstract
In this report we investigate the possibility that the strong claim of Articial
Life might be realized in a situated system. We begin by surveying the current
criticisms against the strong claim of ALife for the case of non-situated systems.
We nd that the refutations of these claims necessarily depend on relativistic
arguments, and when we move from situated to non-situated systems, such relativistic notions lead us to question the possible relationships that might develop
between a situated system and the physical world. Three such relationships are
delineated: a sociological relationship, an engineering relationship, and a biological relationship. From the discussion of these interrelations, it becomes clear that
situated systems that interact with terrestrial life have the highest probability
of being considered living systems.
\The cyclone had set the house down in the midst of
a country of marvellous beauty. While she looked eagerly
at the strange and beautiful sights, she noticed coming
toward her a group of the queerest people she had even seen."
The Wizard of Oz, L. Frank Baum
Introduction
Perhaps the grandest claim of the ALife literature is that propounded by the eld's founder
(Langton 1996)1: computers can be used not only to simulate life, but to synthesize it. It is
hoped (Langton 1996; Ray 1992) that such a synthesis might lead to a `comparative biology',
by which the necessary and universal properties of all living systems can be determined.
[email protected]
1
Originally appeared as a paper in (Langton 1989).
1
In two previous essays (Bongard 1999a; Bongard 1999b)2, we have surveyed criticisms
raised this claim. These criticisms can be divided into two camps. In the rst camp, researchers argue that the act of measurement is a prerequisite function of any living system
(Pattee 1989; Cariani 1989). If measurement is viewed as a mapping from a non-symbolic to
a symbolic system, then a computer simulation can never realize a measurement because a
computer can only operate on formal symbols, which are already the result of some measurement. In the second line of argument against strong ALife (Emmeche 1992), if one believes
that life is not exclusively based on a substrate-independent, Platonic form, then life cannot
be completely separated from its material substrate. Therefore, it is argued, life cannot
be instantiated in a computer or other formal system that is not built from the relevant
material (Emmeche 1992: 473).
We have put forward rebuttals of both these lines of argument. In (Bongard 1999a), we
showed that coevolution leads to continual semantic emergence: populations continually discover new ways of measuring the changing dynamics in the external environment, which are
caused by coevolving populations. In (Bongard 1999b), it was argued that from among the
possible denitions of life, the most promising denitions are those that are based primarily
on an aggregate3 and only secondarily on the organisms in the aggregate. (One example
of this kind of aggregate denition|supple adaptation|is given in (Bedau 1996).) Thus,
when instantiating a system in a computer simulation, as long as the necessary relations are
preserved among the entities in the aggregate when they are simulated, it would be possible
to instantiate a living system within a computer simulation.
Both of these rebuttals, it can be seen, are relativistic. Coevolutionary measurement
demands an emphasis on the relations between populations, and how those relations allow
populations to measure changes in other, coevolving populations. An aggregate denition of
life requires investigation into the interrelations between organisms, coevolving populations,
and an organism and its abiotic environment which are necessary for a population to be
considered alive.
In this report we turn our attention from non-situated to situated systems, and ask
whether a robot population4 could ever be considered to be a living system. In the next
section, we will outline our approach to this question, and survey the possible relationships
that could hold between a robot population and the physical world. In the penultimate
section, we explore the autonomy that a robot populations might achieve, and how this
would bear on the purported vitality5 of such a population. In the nal section we summarize
our ndings.
Articial and Natural Systems
If we consider embodied, situated systems, the future synthesis of a living system is not
guaranteed. Although the arguments of Cariani and Pattee collapse if we stipulate a robotic
population (of sucient morphological and sensory plasticity) that can evolve new measurements of the external, non-symbolic world, the claim that a living system is grounded in
some way in carbon-based chemistry still presents a challenge.
In the introduction, we showed how relativistic arguments can be used to rebu criticisms
of the strong claim of ALife for non-situated systems. We can again employ relativistic arguments to clarify the claims of strong ALife for situated systems. In order to do this, however,
2 This report does not regurgitate material from this previous work; rather, results obtained there are
used as a starting point for discussion.
3 We use the term aggregate as opposed to population in order to clarify the point that an aggregate is not
simply composed of a set of organisms, but also contains the relevant features of the organisms' environment
that are necessary to view the population as a living system.
4 Henceforth we use the term robots, or robot population as shorthand for an articial, embodied and
situated system.
5 The use of the term vitality is restricted in this essay to the degree to which an articial system can be
considered a living system.
2
we can no longer restrict our discourse to the possible interrelations between entities within
a formal system: we must now investigate the relationships that could exist between a robot
population and the natural world. We postulate three such types of relationships: those
between a human population and the robot population; those between a robot population
and some real-world task domain; and those between a robot population and terrestrial life.
Sociological Relationships
Consider a robot population that interacts with a human population. The relationship could
be of a practical nature, in which robots aid humans to accomplish some physical task, or
the relationship could be of a more cultural, humanitarian, creative or spiritual nature. We
reserve the former type of relationship for the following subsection.
In the latter case, we can postulate robot artisans, robot psychologists, robot academics,
et cetera. It becomes clear that these types of robots would interact with humans in a
sociological context: relationships between humans and robots would be based exclusively
on human interests, goals and ideals. It would follow from this that the intelligence of such a
system, as opposed to its vitality, would be of primary concern. However, this essay focusses
on the claims of strong ALife; analysis of the sociological relationship between a human and
robot population falls under the aegis of strong AI, and will thus not be further pursued
here.6
Engineering Relationships
As opposed to the types of robot populations hypothesized in the previous subsection, in this
subsection we consider robots that perform some task in the physical world: space station
construction and house cleaning are two such examples.
In exploring the question of whether robots of this type could ever be considered alive, we
must reconsider the criticisms against non-situated systems. In response to the arguments
of Cariani and Pattee, we stipulate that such a robot population must be dedicated to a
suciently complex and dynamic task: the task must be complex enough so that a prespecied set of sensors and eectors are not sucient to accomplish the task; and dynamic
enough to stimulate continual development of new types of sensors and eectors. In this
way, a task of this type would stimulate the robot population to continually create new
methods of measurement, and would thus exhibit semantic emergence, two properties that
Cariani and Pattee require of a living system.
The second line of argument against the strong claim of ALife|the necessity of organic
matter in the matter/form duality of living systems|requires more thought. In order to
address it, we adopt a Heideggerian view of objects in the world with which human experience
comes in contact:
\According to Heidegger, the fundamental character of the entities with which
Dasein7 has dealings in everyday practical activity is that of equipment. We
encounter entities as being for, for instance, throwing, writing, transportation,
or working." (Wheeler 1996: 226)
From this, we view the robot population geared towards a specic task as a type of tool,
or as a type of Heideggerian equipment: the status of the population is derived from its
functionality. Thus, the material from which a robot population is constructed is secondary
only to how it performs in accomplishing its specied task.
6 If one takes the stance that being alive is a prerequisite for intelligence, then the classication of a robot
population as intelligent would concomitantly require the robot population to be considered alive. Thus,
such a relationship could indirectly bear on the strong claim of ALife for such systems.
7 \This entity which each of us is himself and which includes inquiring as one of the possibilities of its
Being, we shall denote by the term `Dasein'." (Heidegger 1926: 27)
3
However, this does not seem to take us any closer to the possibility of the vitality of
such a robot population: many tools in the real world can be constructed from dierent
materials, and still perform the same function equally well (Sober 1992: 363). Yet Heidegger's emphasis on function, captured in the notion of the ready-to-hand (Heidegger 1926:
98), does help us to bypass the requirement for an articial living system to be built from a
particular material substrate. We can do this by demanding that such an articial system
must exhibit some function deemed necessary of a living system: for Cariani, this function
is semantic emergence; for Pattee, it is mapping non-symbolic entities to symbolic entities;
for Bedau (1996), it is supple adaptation. In this way, if we adopt both Heidegger's stance
of the primacy of functionality for equipment|in this case, a robot population|and some
denition of life that stipulates the system exhibit a particular type of function, then we can
see that it might be possible to imagine a robot population that could be considered alive.
For example, if we adopt Bedau's supple adaptation denition of life, then a hammer, which
is multiply realizable (i.e., can be constructed from dierent material substrates without
aecting its function), is not alive: however a hammer population that reproduces, and over
time produces hammers adapted to the size of nails in the hammer population's immediate
environment, may be considered alive.
As the hammer example makes clear, this type of stance does not seem very satisfying.
In the next subsection however, we introduce another type of relationship possible between
a robot population and the physical world, and use a corollary of Heidegger's functionalist
viewpoint to sharpen our investigations into the possibility of a situated, living system.
Biological Relationships
Consider now a robot population that interacts with terrestrial life in some way: some
examples might include articial bees that help bees to locate food sources and potential
hive sites; or articial sh that lead natural schools of sh into shing nets. It seems that
this type of robot population has a much better chance of being considered alive, but our
previous discussion suggests caution: we must investigate how such articial and natural
populations interact before we can decide on the articial population's vitality.
Noble (1997) argues that the scientic validity of Articial Life rests on its ability to
generate hypotheses by computer simulation, which are then amenable to testing in the
physical world. Specically, a set of axioms implemented in a model, AM , should generate
a set of emergent phenomena EM in the model. If EM are suciently similar to some
phenomena in the the real world, ER, then it is possible that AM are a good explanation of
the real-world axioms AR that give rise to ER . Although Noble's argument is aimed at nonsituated systems, we can apply it to our current situation: if we introduce a robot population
into a natural ecology, and the ecology and robot population interact in a suciently natural
way8, then EM ER . From this we may infer that AM AR , and, if some of the axioms in
AR include necessary functional conditions for life (such as Pattee's measurement condition,
or Bedau's supple adaptation condition), we may conclude that the robot population is also
exhibiting these conditions, and is therefore alive. From this, we see that the degree to
which a robot population becomes subjugated to the normative ecological dynamics of the
natural living system into which it is placed determines the robot population's vitality.
If we again view the robot population as a type of Heideggerian equipment, the importance we place on the type of relationship between a natural and robot population dovetails
nicely with the argument that Heideggerian equipment is transparent to the viewer as long
as it successfully fullls, and continues to full, the function attributed to it (DiPaolo 1998:
61; Merleau-Ponty 1962: 143). In other words, the continued normativity of the ecological
dynamics of a natural living system after a robot population has been introduced reects the
degree to which the robot population exhibits functionality deemed necessary of life, such
We view `natural' here as a predetermined set of normal ecological relationships, such as niche creation,
resource competition, etc.
8
4
as dynamic measurement or supple adaptation. From this, as in the previous subsection, we
can see that if we adopt the stance of viewing a robot population as a type of Heideggerian
equipment, and adopt one of the available denitions of life (such as measurement or supple
adaptation), we are able to postulate some future robot population that could be considered
alive.
However, we still are confronted with the material argument (Emmeche 1992) against
the strong claim of ALife. Yet unlike the case of an engineering relationship between a robot
population and the physical world, the biological relationship aords an interesting response
to the material argument. It may be possible to postulate a robot population that evolves
a parasitic relationship with a natural species: a natural species may come to provide the
robot population with those functions which require a biochemical substrate.
For instance, if we take the view that metabolism is a necessary criterion for life (Boden
CSRP482), then a robot population might evolve in the natural world that relies on a natural
species to perform catabolism and anabolism on its behalf. In this way, if we stipulate that
life requires some dependence on a biochemical substrate, this stipulation may still be met
by an articial, situated system, albeit indirectly.
Autonomy and Situated Systems
In the previous section, we surveyed the various types of relationships that might exist
between a robot population and the physical world. From this analysis, we have been
able to determine whether, or what types of robot populations might be classied as alive.
However no discussion of the vitality of a system would be complete without some discussion
of how autonomy within such a system informs its qualication of being alive. Boden
(1996) delineates three dimensions along which autonomy might be explored; we shall here
concentrate on autonomy as the \extent to which the controlling mechanisms [of behaviour]
[are] self-generated rather than externally imposed." (p. 102).
In a sociological context, the ability of a robot population to respond to, and further
human values serves as a restriction imposed from the external world onto the robot population. A robot population designed to function as artisans would rapidly be decommissioned
if the artwork produced had no aesthetic eect on its human patrons.
In the engineering context, the restriction becomes more stringent: the behaviour of the
robot population is constrained to those behaviours useful or necessary for accomplishing
the set task. Returning to Heidegger, the primacy of functionality dictates that the goals of
such a robotic system|what Cariani (1991: 789) refers to as `pragmatic emergence'|must
come from the external world:
\Contrary to what people in the eld of traditional AI have proposed ...
`functions' may not be some additional property attached to an object, but at
the very heart of what things actually are. The system engineer must design this
functional world and the autonomous system's goals (yielding hetero-nomous
instead of auto-nomous behaviour)." (Prem 1997: 12{13)
.
In the case of a robot population interacting with terrestrial life, some of the functionality
that must be imposed on more task-oriented systems can be withheld. In the limiting case,
our only requirement of a robot population in a biological context might be that it survive
in competition and cooperation with the natural species around it. In such a context, the
autonomy of a robot population would be identical to that of a natural population: each is
beholden to the demands placed on it by the physical world (for example drought or regular
periods of darkness) and the ecological niche to which it has adapted (such as competition
for resources or limited mobility). It may be that natural and robot population respond
dierently to these restrictions, but this does not aect the degree of autonomy attributed
to these two types of populations.
5
Thus we see that the highest degree of autonomy can be achieved by robot populations
which interact with biological systems. If we equate autonomy with living systems, this supports the conclusions reached in the previous section, in which robot populations interacting
with terrestrial life are most likely to be viewed as living systems in their own right.
Conclusions
In this report, we have examined the possibility of building a situated, embodied system
that could be considered alive. Like the case of non-situated systems, criticisms against the
strong claim of ALife have required the adoption of a relativistic viewpoint. In the case
of non-situated systems, this required an analysis of the relations between entities within a
formal system such as a computer.
For the case of situated systems, it was necessary to delineate the types of relationships
that could exist between a robot population and the physical world. Three such relationships
were dened: a sociological context, in which robots interact with humans at a cultural,
aesthetic or intellectual level; an engineering context, in which robots are applied to some
real-world task; and a biological context, in which robots interact with terrestrial life.
It was found that the vitality of any situated system was dependent on the nature of
interrelations within these dierent contexts, and also on what necessary conditions for life
are adopted. From our analysis, it was found that robots interacting with terrestrial life hold
the most promise for being considered alive. Such an articial population could integrate
into the normative dynamics of a given ecosystem; satisfy the dependence on a biochemical
substrate, if such a dependence is deemed necessary for life; and achieve the highest degree
of autonomy.
Unfortunately, the fact that a robot population tightly linked to terrestrial life has the
greatest chance of being classied as a living system deates the hopes that ALife may serve
as a comparative biology, as postulated by Langton (1989) and Ray (1991). The constraints
placed on such an articial system by its terrestrial, biological context would preclude any
conclusions being drawn from the articial population's dierences and similarities to terrestrial life.
Despite this negative conclusion however, this essay has shown that the possibility of
realizing an articial, situated, living system may be a future possibility: it is predicted
that the realization of this goal alone will go a long way towards a richer understanding of
terrestrial life.
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6
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