15 February 2020 | New Scientist | 37corrupted information about the future,
thanks to prediction from patterns in the past
and present. Does agency in some way consist
of an ability to harness and combine these
different forms of information – and if so,
can we develop a mathematical language to
express their differences? Carroll is working
on that. “I think that I have ideas and I’m on
the right track for understanding,” he says.
“But the i’s have not yet been dotted.”
Others are scratching around the same
territory. “Agents are just creatures that can
learn about the world and use what they learn
to change and control it,” says Susanne Still
at the University of Hawaii. “They follow rules
of information acquisition, so we need to find
out what those rules are.”
Those rules must fulfil certain criteria.
They must include some element of memory
storage and recall: the ability to bank and
process external information over time so
as to project it onto the future. They must
allow for feedback loops, so relevant new
information can update information already
held internally. There must also be a way of
delineating an agent’s boundary, to distinguish
actions triggered internally from those
triggered externally.entropy in contravention of the second law.
Subsequent investigations showed that
it was clever manipulation of information
that gave “Maxwell’s demon” this apparently
unphysical power. Much more recently,
physicists including Paul Davies at Arizona
State University have suggested that
information manipulation might be what
distinguishes living matter from inert matter.
It almost certainly has a bearing on agency.
A curious physical fact is that we have access
to detailed information about the past, in the
form of our memories and other evidence,
and also more limited, unreliable andHELLO WORLD/GETTY IMAGES“ Our agency is
time-oriented:
we can change
the future, but
not the past”
>conscious world, let alone how those states
interface with the wider world. “It’s one
thing to say I can explain the temperature
and density of the air by hypothesising
that it is made of molecules bumping into
one another,” says Carroll. “It seems quite
a more dramatic project to say I can explain
mind and choices and consciousness as
emerging out of atoms and molecules
bumping into one another.”
But just as we don’t need to know
how every molecule in a gas is moving to
know its temperature, so agency might be
understood by skating over its interior details
and finding global quantities that correspond
to measurable outcomes. “I want to somehow
find the minimal intellectual tools for
understanding how something can work
that you would describe as an agent and still
be compatible with physics,” says Rovelli.
A matter of time
We have at least one big clue where to dig:
the way agency changes the future, but not the
past. “We think of agency in a time-oriented
way,” says Rovelli. “We do something and
then something happens.” Most physical
laws don’t work like this: the basic equations
of classical and quantum physics run just as
well backwards as forwards.
The only one-way street in physics is
the inescapable rise of disorder, or entropy.
This is encapsulated by the second law of
thermodynamics, the empirical law that
says ice creams melt, milk can’t be unspilled
and that it is far easier to lose one sock than
to unite a pair. “That’s one of the steps to
clarify to unravel this problem,” says Rovelli.
“How do entropy and the second law of
thermodynamics come in?”
Rovelli, Carroll and others are attempting
to find out by sketching the possible
connections between agency and wider
cosmic flows. Carroll admits that there is still
a lot of groundwork to be laid. “How do you
even translate concepts like ‘make a decision’
or ‘choice’ or ‘cause something to happen’
into the language of statistical mechanics
where you have things bumping into each
other and probability distributions and stuff
like that?” he asks.
Hidden away in these thermodynamic
considerations is the concept of information.
A century and a half ago, physicist James Clerk
Maxwell imagined a tiny intelligent being that
could gauge the speed of individual molecules
in a gas to sort hotter ones from cooler ones,
and so apparently decrease disorder and
Ice creams don’t
choose to melt –
but we choose
to buy oneJim Al-Khalili will shine a light on the most profound insights revealed
by modern physics at an evening lecture in London on 11 March
newscientist.com/events