1 Causation as Folk Science John D. Norton Center for Philosophy of science Department of History and Philosophy of Science University of Pittsburgh CARL.

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Causationas Folk Science

John D. NortonCenter for Philosophy of science

Department of History and Philosophy of ScienceUniversity of Pittsburgh

CARL FRIEDRICH VON WEIZSÄCKER LECTURESUNIVERSITY OF HAMBURG

June 2010

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Principal Claims

Negative Thesis Denial of causal fundamentalism, which asserts that the world is governed by a principle of causality;based on a dilemma.

Positive Thesis Sciences restricted to hospitable domains adopt forms of various folk sciences of causation, which explains the prevalence and utility of causal notions.

Modern Physics Causal anti-fundamentalism is compatible with the widespread presence of causal terms and principles in modern physics.

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Guiding Intuitions

NegativeCausation is about the physical connectedness of things in the world. Its analysis is the province of science and not a priori postulation.

PositiveCausal notions are pervasive because, whatever the domain, we are plastic enough and inventive enough to find relations we are comfortable to label “causal.”

Modern philosophical literature in causation has lost its way.It is devoted to finding out precisely what we mean when we say C causes E; and mistakes that for finding out deep truths about the connectedness of things in the world.

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Negative ThesisCausal Anti-fundamentalism

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Causal Fundamentalism: the doctrine

Nature is governed by cause and effect; and the burden of individual sciences is to find the particular expressions of the general notion in the realm of their specialized subject matter.

Unity of meaning of causal talk in different domains.

Causation is about the connectedness of things in the

world.

There is a universally applicable principle of causality.

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Causal fundamentalist's dilemma

EITHER (first horn)

Conforming a science to cause and effect…

OR (second horn)

We must find some restriction that can be properly applied to all sciences.

No appropriate restriction; no enduring principle of causality.

The imposition of the causal framework makes no difference to the factual content of the sciences,

It is an empty honorific.

…places a restriction on the factual content of a science

…it does not place a restriction on the factual content of a science.

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First hornHow might causation restrict the factual content of a science?

20th c. Principle of common cause Fails for entangled states in quantum theory

4th c. BC. Aristotle’s four causes.Material, formal, efficient, final.

17th c. mechanical philosophy. No place for final causes.

17th c. Newton. Action at a distance?“…so great an absurdity that no man, who has in philosophical matters a competent faculty of thinking, can ever fall into it.”

18th, 19th c. No mechanism found; no finite velocity measured; no shielding. Gravity is action at a distance.

20th c. Probabilistic account of causation. Virtually all physical theories indeterministic. No probabilities for undetermined outcomes. Even Newtonian physics!

19th century purification of causation.No agents/patients, continued existence of cause. Causation is determinism. Causes guarantee effect.

20th c. Quantum theory. Physics supplies probabilities only of effects.

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Second hornWhat if causation places no factual restriction on science?

Any possible science, no matter odd, may be conformed to causation.

“Nature is governed by cause and effect;

and the burden of individual sciences is to find the particular expressions of the general notion in the realm of their specialized subject matter.”

…but it is no way restricted by it.

…so the burden consists solely in assigning honorific, causal labels.

…so it does not tell us about the world, but about our definitions and or own psychology.

Principle of causality“…is an analytic consequence of what is commonly meant by ‘theoretical science.’”“…maxim for inquiry rather than a statement with definite empirical content.” Nagel

Causation as indispensable to science. (Kant, Nagel, …)

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Humean/Positivist skepticism

Anti-metaphysical.Epistemically pessimistic.Skeptical of content of science beyond observation.Causation just is constant conjunction, functional dependence of facts.

Varieties of causal skepticism

(Weaker) EliminativismRussell: “…oddly enough, in advanced sciences such as gravitational astronomy, the word ‘cause’ never occurs…”

Mach: “…science of the future will discard the idea of cause and effect as being formally obscure.”

Anti-Fundamentalism

Anti-apriori.Epistemically optimistic.Science makes discoveries beyond observation.Causation is an attempt to preempt discovery.

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Positive ThesisCausation as Folk Science

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Generative capacity of reduction relations

General relativity:fundamentallygravity is not a force, but a manifestation of the curvature of spacetime.

restrict to weak fields, non-cosmic scales

Gravity behaves just like the force for which Newton found powerful evidence.

Gravitational forces, heat as caloriccan be pervasive and useful notionswithout being fundamental.

…we require the same of causal relations.

Statistical physics:fundamentallyHeat is just a disorderly distribution of energy.

restrict to systems that do not exchange heat and work

Heat behaves just like the conserved fluid “caloric” of Lavoisier and Carnot.

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Generating causation

Greater sciencenot fundamentally causal

restrict to ordinary Newtonian systems of finitely many degrees of freedom

DeterminismPresent state

causes future via forces

restrict to vacua surrounded by fluids

Vacua have active powers. They suck.

restrict to dissipative systems

States of lowest energy, highest

entropy are final causes

Sense of causation recovered in each domain is different.

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Analogies to reduction relations in science

Folk theories of causation are warranted as physical theories in so far as they capture the relevant physical content of the embracing theory.

Folk theories of causation are attractive for their ease of comprehension and ease of use.

Different notion of causation recovered in different domains.

Folk theories tend to be less precise than the corresponding scientific theories.

Disanalogies to reduction relations in science

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Are causes real?

Strong fictionalism.Nothing is real unless it is in the ontology of the final science.

Inscrutability. Infinite regress.We will never know that we know what is real.

Qualified prudent realism.Entities of present theories are real in so far as they are structures licensed by further science.

It is a real property of spacetime that its curvature sometimes manifests as a force.It is a real property of random energy distributions that they sometimes manifest as a conserved fluid.

Strong realism.Every entity of a functioning science should be construed literally.

Heat is NOT a conserved fluid; it just behaves like one sometimes.

Causes are as real as gravitational forces and caloric.

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We see faces and figures in clouds…

Fundamentally, there are no faces and figures there.

We all see them.

The shapes are real in the sense that the nose really is a lobe of nose-shaped cloud

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Modern Physics and Causal Anti-fundamentalism

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Is there a Contradiction…?

1. Talk of causal relations and causal principles permeates the fundamentals of modern physics;

2. Causal anti-fundamentalists do not believe that the world is governed by a principle of causality.

There is not. The causal talk pertains to contingent features of modern physical theories that are not manifestation of a deeper causal necessity.

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The causal notions and causality conditions of modern physics express:

2. Propagation of matter in spacetime must conform

to the lightcone structure. “No propagation outside the light cone.”

These are contingent facts about the world. Physical theories without them can be quite cogent. They are not metaphysical necessities.

1. The existence of a finite, invariant velocity in spacetime

= spacetime has a light cone structure

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Illustrations in Relativity Theory

Special relativity

Causally connectible = timelike or lightlike connected(+ numerous variant forms)

General relativity

“local causality” = Laws governing matter fields are such that there is no propagation outside the light cone. The condition is formulated more exactly in terms of a Cauchy problem for the differential equations governing the matter fields. (p. 60)

“causality condition” holds holds if there are no closed non-spacelike curves. (p. 190)

Global extensions

"The strong causality condition is said to hold at p if every neighbourhood of p contains a neighborhood of p [sic] which no non-spacelike curve intersects more than once." (p. 192)

"Stable causality condition ... [informally] one can expand the light cones slightly at everypoint without introducing timelike curves." (p. 198)

S. Hawking and G. F. R. Ellis. The Large Scale Structure of Spacetime.

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Illustrations in EPR/Quantum Theory

"Locality Principle (L)

Elements of reality pertaining to one system cannot be affected by measurements performed 'at a distance' on another system.”

"For Bell locality, 'at a distance' means in the absence of causal influences recognized by current physical theories.”

“For Einstein locality, 'at a distance' means at a space-like separation between the space-time locations where the element of reality pertaining to one system exists and the measurement on the other system takes place.”

M. Redhead, Incompleteness, Nonlocality, Realism. p. 75

This principle is not offered a principle of quantum theory, but as part of an expressed hope that quantum theory will conform to it. It may fail to, as happened with the common cause principle.

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Illustrations from Quantum Field Theory

Wightman axioms

"E. Causality.The fields shall satisfy causal commutation relations of either the bosonic or fermionic type. If the supports of the test functions f and h are spacelike to each other then either

[i(f), j(h)] = 0

or

[i(f), j(h]+ = 0”(I.e. measurement on one field operator has no effect at events spacelike separated from it.)

"G. "Time-slice axiom." "Primitive Causality""There should be a dynamical law which allows one to compute fields at an arbitrary time in terms of the fields in a small time slice...[formula for time slice]”(I.e. propagation of field operators akin to propagation of ordinary fields that admit well posed Cauchy problem, domains dependence, etc.)

R. Haag, Local Quantum Physics: Fields, Particles, Algebras. p.57

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Reichenbach's common cause principle

It is really a rule for detecting causal connections without defining what that connection is.

It is not a principle that defines the nature of causation.

It is a fallible rule and so not suitable for a definition.A correlation between A and B can be screened off by conditionalizing on C licenses the inference that C is the common cause of A and B. But there remains a very small but non-vanishing probability that A and B may be interacting causally nonetheless.

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Peaceful Harmony

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Causal talk in modern physics…

… does not conform to the first horn (causal principle as universal factual restriction).

… does conform to the second horn (causal talk as honorific).

It does not supply a contingent, universal causal principle. Otherwise all physical theories that do not explicitly invoke conformity to a light cone structure would be deficient causally.

Newtonian mechanics was not causally deficient, just odd.Sciences can invoke causation without making explicit use of the lightcone structure of spacetime. (Geology)

The complaint that processes violate causality requirements in modern physics is not a complaint that they violate some overarching metaphysical principle.

It is an abbreviation for the objection that they do not respect the light cone structure spacetime is known empirically to have.

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An Independent Principle of

Causality in Electromagnetic Scattering?

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Scattering from a dielectricIncident plane wave approaches from left…

…excites dielectric atom and generates scattered field…

…and passes.

Frames from animation at http://www.met.rdg.ac.uk/~swrhgnrj/maxwell/circle3.html

Total field (incident plus

scattered)

Scattered field (total minus

incident)

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Basic Physics of Scattering

€

scattered(x, t) = G(x, t)−∞

∞∫ ⋅incident(x, t − t ' )dt '

Scattered field at position x

is a linear sum ofincident fields at same position x and other times

No influence from future (“NIFF”).

G(x,s)=0 for all s<0.Hence incident can only contribute to scattered fort-t’>=0i.e. t’<t.

How do we arrive at this relation?

(“LIN”)

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… Use the Principle of Causality

Mathias Frisch

J. D. Jackson, Classical Electrodynamics

NIFF… “is an accord with our fundamental idea of causality in physical phenomena”

LIN+NIFF is… “the most general spatially local, linear, and causal relation can be written between [scattered] and [incoming] in a uniform isotropic medium. Its validity transcends any specific model of [the dielectric].”

Final results are “are of very general validity, following from little more than that assumption of the causal connection [LIN] betweed [scattered] and [incoming].”

…and similar remarks from others.

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… Use the Principle of Causality

Mathias Frisch

Frisch:

“…now we postulate an additional constraint on all causally possible models that

an effect cannot temporally precede its cause…”

“It might in fact be true that effects never precede their causes. But I think that we can allow for the possibility that a certain causal condition is not true in general and nevertheless take it to be physically well-founded.”

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First, Jackson computes a simple model of the dielectric by ordinary methods and finds it conforms with NIFF. (Time reversals of ordinary scattering precluded by choosing the boundary condition of dielectric charges initially at rest.)

Then, Jackson finds more general cases too hard to compute, but he expects nonetheless that the final result would still conform with NIFF if only we do all the sums.

Awkward… so he proclaims NIFF fits with “causality.”

No precise principle of causality is formulated or applied to arrive at NIFF.

Not clear that Jackson does use an independent principle of causality.

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Principle: “An effect cannot temporally precede its cause.” may hold only some times. When?

Not clear that Jackson could use an independent principle of causality.

If only for scattering, then we are merely restating NIFF.

If more broadly, then to which processes does it apply?Why is this any better than “it applies except when it doesn’t”?

Literature that admits backwards causation in physics:time travel, tachyons

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How could a principle of causality pick out the “true” forward direction?

Time reversibility of electrodynamics.

Any feature of “forward” system has a perfect correlate in the “reversed” system.

Forward ReversedReversed Forward

Add a factual time direction to spacetime?

… but both processes assembled from pieces that are locally time reversible. Allow them locally but prohibit assembly?

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What precisely does the principle of causality say?

Must be precise enough to be applied in a computation in mathematical physics.

“An effect cannot temporally precede its cause.”

Which state is the effect and which the cause, in any process with states that evolve over time?

The cause comes earlier? That makes the principle true by definition.

What counts as a cause? An effect?

States over time? At an instant? Which hypersurface of simultaneity?

What sorts of processes are properly causal?

“Causal” means later states depend on earlier?What of Lagrange principles that pick out motions by extremizing the entire history?

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Conclusion

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Principal Claims

Negative Thesis Denial of causal fundamentalism, which asserts that the world is governed by a principle of causality.

Positive Thesis Sciences restricted to hospitable domains adopt forms of various folk sciences of causation, which explains the prevalence and utility of causal notions.

Modern Physics Causal anti-fundamentalism is compatible with the widespread presence of causal terms and principles in modern physics.

Failure of any stable, factual principle of causality to emerge from our science.

Folk sciences generated by same mechanism that gives us gravitational forces and caloric.

Causal talk arises as part of assuring that processes respect the light cone structure of spacetime.

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