Lecture 2: free will
— the physics of unfreedom: determinism and causality
— quantum mechanics to the rescue?
— Hume
— Dennett
— Wegner
where do intentions come from?
The sense of agency is caused by the functioning of corollary discharge
circuits in the brain, beginning with an intention to act. But what causes
the intention?
slide 2
intuition about intention
Commonsense intuition tells me that my intention to raise my arm,
which can be causally effective (try it), must itself be uncaused — that
is, not entirely determined by my own past history, let alone by factors
outside of myself — if I am to be considered a free agent.
This notion of freedom is, of course, just an intuition, and so should be
distrusted as a matter of principle. Let us examine it in the light of the
laws of physics, and of computation.
slide 3
the physics of freedom
The behavior of any physical system (which is completely describable in
terms of a trajectory through the system's state space) depends on two
properties of its dynamics:
— determinism;
— causality.
slide 4
determinism
A pinball machine is a classical deterministic dynamical system (a system whose state changes
over time according to a rule that is defined in terms of the current
state).
determinism...
Because a pinball machine is deterministic, given the
current position and velocity of the ball, it is possible to predict
its future position and velocity as long as the system remains closed.
The prediction can be extended across the player's actions, if the
forces and the durations of the latter are completely specified.
slide 6
determinism... and causality
Because a pinball machine is deterministic, given the
current position and velocity of the ball, it is possible to predict
its future position and velocity as long as the system remains closed.
The prediction can be extended across the player's actions, if the
forces and the durations of the latter are completely specified.
This system is also causal: for each event, such as the ball
striking a particular lever, it is possible to identify antecedents
without whose occurrence the event in question would not have
happened.
slide 7
determinism... and causality = unfreedom
Because a pinball machine is deterministic, given the
current position and velocity of the ball, it is possible to predict
its future position and velocity as long as the system remains closed.
The prediction can be extended across the player's actions, if the
forces and the durations of the latter are completely specified.
This system is also causal: for each event, such as the ball
striking a particular lever, it is possible to identify antecedents
without whose occurrence the event in question would not have
happened.
The combination of determinism and causality clearly spells the
opposite of freedom for a pinball machine. If brains are deterministic
and causal in the same way pinball machines are, it would seem that
free will is a physical impossibility.
slide 8
quantum mechanics: a way out?
slide 9
quantum mechanics: a way out? 'fraid not.
— quantum mechanical effects are irrelevant at the level on which
brain computes the mind;
— randomness is not freedom anyway.
slide 10
quantum mechanics: a way out? 'fraid not.
— quantum mechanical effects are irrelevant at the level on which
brain computes the mind;
— randomness is not freedom anyway.
A real way out: follow Hume (A
Treatise of Human Nature).
slide 11
following Hume: step 1
Whatever capricious and irregular actions we may perform;
as the desire of showing our liberty is the sole motive of our
actions; we can never free ourselves from the bonds of necessity. We
may imagine we feel a liberty within ourselves; but a spectator can
commonly infer our actions from our motives and character; and even
where he cannot, he concludes in general, that he might, were he
perfectly acquainted with every circumstance of our situation and
temper, and the most secret springs of our complexion and
disposition. Now this is the very essence of necessity, according to
the foregoing doctrine.
We feel that our actions are subject to our will on most occasions, and
imagine we feel that the will itself is subject to nothing; because when
by a denial of it we are provok'd to try, we feel that it moves easily
every way, and produces an image of itself even on that side, on which
it did not settle. This image or faint motion, we persuade ourselves,
cou'd have been compleated into the thing itself; because, shou'd that
be deny'd, we find, upon a second trial, that it can. But these
efforts are all in vain.
slide 12
following Hume: step 2
As to causation; we may observe, that the true idea of the human
mind, is to consider it as a system of different perceptions or
different existences, which are link'd together by the relation of
cause and effect, and mutually produce, destroy, influence, and
modify each other. Our impressions give rise to their
correspondent ideas; and these ideas in their turn produce other
impressions. One thought chaces another, and draws after it a
third, by which it is expell'd in its turn.
In this respect, I cannot compare the soul more properly to any thing
than to a republic or commonwealth, in which the several
members are united by the reciprocal ties of government and
subordination, and give rise to other persons, who propagate the same
republic in the incessant changes of its parts. And as the same
individual republic may not only change its members, but also its laws
and constitutions; in like manner the same person may vary his
character and disposition, as well as his impressions and ideas,
without losing his identity. Whatever changes he endures, his
several parts are still connected by the relation of causation.
slide 13
the Humean middle way
The resolution of the problem of free will — finding a middle way
between chance and determinism — lies in pursuing the Humean analogy
between the
Self and a self-governed
republic.
The Self, construed properly as a causal network distributed in space and
time, has all "the varieties of free will worth wanting" (Dennett, 1987).
[The boundaries of the mind are] far enough back to give my
self enough spread in space and time so that there is a
me for my decisions to be up to!
— Dennett (2003)
slide 14
individual decisions are neither random nor uncaused
Unlike in a pinball machine, causality in a high-dimensional dynamical
distributed system consisting of one or more brains (each with its
history of past interactions with the world) and their environment is
extremely complex.
Among the multitude of factors affecting an outcome, some may be
random, but for consequential outcomes most are not. In a natural
cognitive system, moreover, a significant subset of the non-random
factors that affect consequential outcomes are part of the system
itself (which is distributed in space and time).
There is a very simple reason for this: evolution.
slide 15
evolution ensures that individual decisions are attuned
to individual needs
A system whose behavior is less random and more in line with the needs
of its survival and procreation stands a better chance of driving
rivals out of its ecological niche. Evolutionary pressure thus works
to concentrate various causal bottlenecks that determine the behavior
of a unit of selection (an individual fertile, gene-carrying organism)
within that unit.
As a result, well-adapted individuals are characterized by a certain
degree of control over their fate, as exemplified by the ability to avoid
an impending event whose potential consequences are projected by the
cognitive foresight mechanism to be harmful.
[Dennett's example in Freedom Evolves: evitability in the game of Life]
slide 16
the paradox of choice and necessity — resolved
I am compelled to choose, but what compels me —
"situation and temper, ... complexion and disposition, ... a system of
different perceptions ... link'd together by the relation of cause and
effect"
—
is me.
slide 17
individual future is subjectively open
My future mind states are not just unknown but unknowable
even to myself except through the regular process of cognition.
This kind of uncertainty about personal future affords me a subjective
freedom.
The intractability of anticipating the behavior of complex
systems implies also that to a cognitive agent the rest of the universe
(including the mind-space trajectories of other agents) is, in the
long run, equally unknowable. The universe as a whole may be
deterministic, but to its denizens the far future is always uncertain.
slide 18
the mind's best trick
Wegner
distinguishes between empirical will (the
distillate of temporally structured statistical relationships between
one's thoughts and actions), and phenomenal will, which is an
illusion generated by the mind to account for one's behavior.
The feeling of free will is thus predicated on the absence of
surprise when the efference copy of a thought or an action originating
in one part of the brain matches the feedback from another.
slide 19
the mind's best trick
In the approach of the Illusion of Conscious Will, the whole idea
of a "person" is an elegant accounting system for making sense of
actions and ascribing them to constructed entities that are useful for
purposes of social justice and the facilitation of social interaction. A
person is constructed in the mind of the person, and, through a variety
of communications and evidences, in the minds of others as well.
— Wegner (2004)
slide 20
free will and the Self
Thus while we would assume that there has to be a self in order for
there to be freedom, Nagarjuna would say that there is freedom only
to the extent that there is not a self.
If we cannot call the karmic web free since it lacks a self, by
the same token we cannot call it determined, since nothing
outside of it is causing it. To the extent that people identify
a self, that self is determined by causes outside of it. The
more cultivated they become on the Buddhist model, the less they
think this way.
The less who thinks this way? A question that the European philosopher
might ask. Nagarjuna's answer is no one, really. The
non-personal web of causes and conditions sheds the delusion, or,
rather, ceases to give rise to it.
— Gier and Kjellberg (2004)
slide 21
gate, gate, paragate...
