Contents - Konrad Lorenz Institute

Steve Stewart-Williams
Darwin and Descartes’ Demon
On the Possible Evolutionary Origin of
Belief in an External World
Without any reasoning, or
even almost before the use
of reason, we always suppose
an external universe
which depends not on our
perception but would exist
though we and every sensible
creature were absent or
annihilated. (HUME 1955,
Section XII, Part I)
Those cousins of our ancestors
who could not manage
to learn that there was
an independently existing
‘external world,’ one whose
objects continued on trajectories
or in place even when
unobserved, did not fare as
well as those who quickly
recognized obdurate realities.
(NOZICK 1993, p121)
How can we be certain
that our senses provide us
with an accurate picture
of the world How can we
be certain that there really
is an objective world
at all, and that all our experience
is not simply a vivid dream or hallucination
These questions relate to one of the most fundamental
and long-standing issues in philosophy:
the problem of justifying belief in an external
world. The goal of this article is not to resolve this
difficult philosophical conundrum. My focus is psychological
rather than philosophical, and I will simply
assume what many philosophers believe is impossible
to prove: that there is an external world,
causing our perceptions and existing independently
Abstract
This article explores the possibility that the tendency
to believe in an objective, mind-independent external
world traces to innate aspects of the human mind. The
aspects of mind in question are, first, the capacity to
distinguish mental states that have objective referents
from those that do not (e.g., perceptual states versus
mental imagery), and second, the capacity to mentally
represent the continued existence of parts of the world
that are beyond the reach of the senses. It is proposed
that the evolutionary function of these cognitive abilities
relates to the production of novel but adaptive voluntary
behaviour. Evidence and arguments are
provided in support of the innateness hypothesis.
Among these is a Chomskyan-style poverty-of-thestimulus
argument derived from the philosophical literature.
The evolutionary account of the subjective-objective
distinction leads to the prediction that, in
conditions of uncertainty, people will tend to err on the
side of assuming the objectivity of their perceptions
and other judgements.
Key words
Evolutionary psychology, external world, innate ideas,
object permanence, objective-subjective distinction,
philosophy.
of them. In making this
assumption so casually, I
am engaging in precisely
the phenomenon that is
the focus of the article.
My contention is that the
most intuitively plausible
position on this issue for
the vast majority of humankind
is metaphysical
realism, the view that
there is an independently
existing external world. A
number of philosophers
have suggested that the
disposition to form this
view is a part of human
nature (HUME 1978;
NOZICK 1993; PUTNAM
1981). In this article, I
provide a preliminary
and highly speculative
sketch of how these suggestions
might ultimately
be placed within an evolutionary
psychological
framework. I explore the
possibility that the assumption
of an external
world relates to certain innate aspects of the human
mind (that is, aspects that were not derived solely
from experience, but can be traced, at least in part,
to information contained in materials of the developmental
process, in particular the genes; for further
discussion of innateness, see STEWART-WILLIAMS
submitted). My goal is not to establish this position
beyond reasonable doubt. I will be content if I can
show simply that the position is not unreasonable,
and provide the groundwork for further discussion.
Evolution and Cognition ❘ 123 ❘ 2003, Vol. 9, No. 2