SCIENCE science.org 4 FEBRUARY 2022 • VOL 375 ISSUE 6580 503PHOTO: CAO YIMING/XINHUA/GETTY IMAGES
ByJohn ZerilliA
mong the various possibilities ex-
plored in David Chalmers’s intriguing
and entertaining romp through phi-
losophy, Reality+, is a kind of deism—
the view that the universe is the work
of an intelligent being who sets its
laws of operation in motion but then declines
to intervene further. Deism was the theology
de rigueur of elite opinion in the late 18th-
century United States. But in Chalmers’s
hands, deism is not quite the view that a su-
pernatural being created the universe. It is
the view that there is “a serious possibility”
that our universe is a computer simulation
run by an advanced civilization.
There are a few strands to the argument, but
the nub of it is that if an intelligent civilization
lasts long enough, it will likely develop
simulation technology and create many
simulated universes inhabited by intelligent
beings. Under minimal assumptions, it can
be shown that these simulated universes will
greatly outnumber nonsimulated ones. Thus,
any extant intelligence has a considerably
greater chance of being simulated than not.
As always, the soundness of the argument
comes down to its premises. It is not clear
that any civilization can survive long enough
to develop simulation technology in the first
place. Furthermore, consciousness may not
be the sort of thing that can be simulated
at all. Or ethical constraints in an advancedlaws. That is why the book could mark a
turning point in educated opinion. It may be
that Chalmers will do for deism what he was
able to do for consciousness: make the idea
respectable again.
There are two reasons why the times may
favor neo-deism. First, Chalmers is not alone
or even the first high-profile secular or atheist
voice to have mooted “simulation theology.”
There are already enough heavyweights
from the worlds of science, big business,
and philosophy to make simulation theology
respectable among an important section of
the intelligentsia. Neil deGrasse Tyson, Elon
Musk, and Nick Bostrom all spring to mind.
Second, computer science has expanded
the horizons of what is considered possible.
Consider that the Enlightenment forerunner
of the simulation hypothesis was a thought
experiment proposed by René Descartes. But
Descartes’s argument trafficked in evil spirits.
Compelling though his meditations may once
have been, their force was bound to wane in a
secular age. Enter virtual reality, its inevitable
improvement over the next few decades, and
the possibility of a Matrix-style immersive
experience, and suddenly Descartes’s “evil
demon” acquires a most contemporary garb.
There is a lot more in this book than
can be conveyed in the space of a short
review. Chalmers has something to say on
most of the “big questions” in philosophy:
on the immortality of the soul
(simulations “may at least make an
afterlife possible”); the freedom of
the will (“the jury is still out”); the
existence of an external world (even
a simulated world would be real; it’s
just that at the most fundamental
level it would be made up of bits
in the simulator’s computer, not
quarks and electrons); and, of
course, the existence of God. He
also considers questions of value
and politics in virtual worlds,
although these are not the most original
parts of the book. While on all of these issues
Chalmers cuts a Gordian knot in writing both
accessibly and illuminatingly, it is the material
in part 3 on the reality of virtual worlds, part 5
on the possibility of consciousness and mind-
body interaction in digital worlds, and part
7 on language and structuralism in physics
where Chalmers breaks new ground.
Chalmers’s Reality+ is sure to roil a good
deal of philosophical banter—and not just in
graduate seminar rooms. More seriously, it
offers a lot for theists, atheists, and agnostics
to ponder as they reassess their already
“considered” views on a well-worn subject. j
10.1126/science.abn2690As virtual reality devices become more sophisticated,
what we consider possible expands.The reviewer is a philosopher at the Institute for Ethics
in AI and the Faculty of Law, University of Oxford, Oxford
OX1 3UL, UK. Email: [email protected]civilization may forbid the running of
simulations containing sentient creatures.
Chalmers considers all these objections
and several more. He concludes that we can
be highly confident that one of the following
three scenarios holds true: (i) we are simulated
entities, (ii) humanlike simulated entities
are impossible, or (iii) humanlike simulated
entities are possible, but few humanlike
simulators will create them. He
calculates the probability of the
first scenario to be at least 25%.
From this it follows that we cannot
be sure we are not in a simulation.
Furthermore, “If the simulation
argument is even approximately
as good as the design argument, it
deserves to be in the pantheon of
arguments for God’s existence.”
Chalmers attained rock-star
status in philosophy during the late
1990s as a defender of dualism, a
metaphysical hypothesis that, at the time,
was considered more or less defunct among
naturalistically inclined philosophers. Dualists
maintain that consciousness cannot be
accounted for in purely physical, materialist
terms (what Chalmers famously dubbed the
“hard problem”). While dualism is certainly
not a mainstream view, it is once again being
taken seriously by a substantial minority
of both scientists and philosophers, in no
small part owing to Chalmers’s distinctive
arguments and thought experiments.
In this latest offering, Chalmers seems to
have come full circle, articulating what he
describes as an entirely naturalistic account
of God—i.e., a god not exempt from naturalReality+:
Virtual Worlds and the
Problems of Philosophy
David J. Chalmers
Norton, 2022. 544 pp.From dualism to deism
PHILOSOPHYA philosopher comes full circle
BOOKS et al.