2010 11 psa montreal explanation and fundamentalism

Philosophy and Quantum Gravity programsExplanation and string theory

The nutshell version of string theorySome case studies of string explanations

Rejoinders and Conclusion

String Theory: Explanation and Fundamentalism

Ioan Muntean

Department of PhilosophyPurdue University–Indiana University, Fort Wayne

Philosophy of Science Association Meeting, Montreal,November 2010

Ioan Muntean String Theory: Explanation and Fundamentalism

Two stancesPhilosophy of Science and String TheoryString metaphysics?

Two pathways towards Quantum Gravity (QG)

1 Find answers (new or right) to perennial philosophicalproblems in QG (“Philosophical centrism”)

2 Analyze QG as scientific theories or, better, programs(“Philosophical analysis”)

1 ambitious and reformist (integrated in a form of scientism).Useful for metaphysics

2 useful in philosophy of science/physics. Can be normative. . .

1 Philosophical centrism

Most QG programs say something special about our oldmetaphysical concepts:

the nature of spacetime, space or timethe measurement problemthe ultimate nature of objects/processes/events in the world

Question Q1

Which Quantum Gravity program provides the best answer to themetaphysical question X?

In most cases, QG are prescriptive in respect of time, space,quantization etc.

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Question Q1

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the nature of spacetime, space or time

the measurement problemthe ultimate nature of objects/processes/events in the world

Question Q1

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the nature of spacetime, space or timethe measurement problem

the ultimate nature of objects/processes/events in the world

Question Q1

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Question Q1

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Question Q1

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Question Q1

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Question Q1

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Question Q1

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Philosophers should be doing this!

Sometimes philosophers help with insights in the problem ofspace, time, change, dynamics, etc.

“General relativity and quantum field theory are based onsome profound insights about the nature of reality. Theseinsights are crystallized in the form of mathematics, butthere is a limit to how much progress we can make byjust playing around with this mathematics. We need togo back to the insights behind general relativity andquantum field theory, learn to hold them together in ourminds, and dare to imagine a world more strange, morebeautiful, but ultimately more reasonable than ourcurrent theories of it. For this daunting task,philosophical reflection is bound to be of help.” (J. Baezin ?

1’. Yet another philosophical centrism

Strengthen an existing metaphysics by interpreting QG

Structural Realism and QGIdentity and individuation of objects and QG (compare andcontrast with QM and QFT)Part-whole relations and QG.

For Structural Realism and QG see ?

Structural Realism and QG

Identity and individuation of objects and QG (compare andcontrast with QM and QFT)Part-whole relations and QG.

Structural Realism and QGIdentity and individuation of objects and QG (compare andcontrast with QM and QFT)

Part-whole relations and QG.

2. Philosophical pathways to QG

Which QG program is the best as a scientific endeavor?

Question Q2

Which QG program is the best in respect of a given virtue V?

Question Q2’

Which Quantum Gravity program has the drawback D?

This is discussed by fewer philosophers ???

I plan to follow something similar here

Question Q2

Question Q2’

Question Q2

Question Q2’

Question Q2

Question Q2’

Question Q2

Question Q2’

Question Q2

Question Q2’

Question Q2

Question Q2’

A narrow scope

I give up the comparative aspects of Q2 and Q2’and focus onone QG program

Question

Is string theory a successful QG program?

Dimensions of success of theories:

1 Empirical confirmation (preferably direct)2 Predictive success (preferably novel)3 Non-empirical virtues: unification, explanation, elegance,

simplicity4 Problem solving (preferably real problems), etc.5 Fecundity6 Meshing well with other scientific theories

None of them is necessary and sufficient.Are these applicable to String Theory or QG in general?ST does not score well on this scoreboard

A narrow scope

Question

A narrow scope

Question

A narrow scope

Question

A narrow scope

Question

Dimensions of success of theories:1 Empirical confirmation (preferably direct)

2 Predictive success (preferably novel)3 Non-empirical virtues: unification, explanation, elegance,

A narrow scope

Question

Dimensions of success of theories:1 Empirical confirmation (preferably direct)2 Predictive success (preferably novel)

3 Non-empirical virtues: unification, explanation, elegance,simplicity

4 Problem solving (preferably real problems), etc.5 Fecundity6 Meshing well with other scientific theories

A narrow scope

Question

Dimensions of success of theories:1 Empirical confirmation (preferably direct)2 Predictive success (preferably novel)3 Non-empirical virtues: unification, explanation, elegance,

simplicity

4 Problem solving (preferably real problems), etc.5 Fecundity6 Meshing well with other scientific theories

A narrow scope

Question

simplicity4 Problem solving (preferably real problems), etc.

5 Fecundity6 Meshing well with other scientific theories

A narrow scope

Question

simplicity4 Problem solving (preferably real problems), etc.5 Fecundity

6 Meshing well with other scientific theories

A narrow scope

Question

A narrow scope

Question

None of them is necessary and sufficient.

Are these applicable to String Theory or QG in general?ST does not score well on this scoreboard

A narrow scope

Question

None of them is necessary and sufficient.Are these applicable to String Theory or QG in general?

ST does not score well on this scoreboard

A narrow scope

Question

Some reasons to . . . love string theory

It solves some problems:

the ultraviolet divergences of General Relativity and ofStandard Model.no dimensionless free parameters.

Is the dominant research program in quantum gravity (QG)Is the (leading?) contender for a theory of everything:

Advertised as: “a single theory that, in principle is capable ofdescribing all phenomena” ((?, ix)).Heavily advertised in popularizing literature, perhaps the bestknown quantum gravity program

Could tell us new stories about the world:

can talk evolution of the universe before the Big Bang(interpreted as a collision of branes)explains facts about black holes, dark matter etc.

But these are promises and prospective undertakings

It solves some problems:

the ultraviolet divergences of General Relativity and ofStandard Model.no dimensionless free parameters.

It solves some problems:the ultraviolet divergences of General Relativity and ofStandard Model.

no dimensionless free parameters.

It solves some problems:the ultraviolet divergences of General Relativity and ofStandard Model.no dimensionless free parameters.

Is the dominant research program in quantum gravity (QG)

Is the (leading?) contender for a theory of everything:

Advertised as: “a single theory that, in principle is capable ofdescribing all phenomena” ((?, ix)).

Heavily advertised in popularizing literature, perhaps the bestknown quantum gravity program

Could tell us new stories about the world:can talk evolution of the universe before the Big Bang(interpreted as a collision of branes)

explains facts about black holes, dark matter etc.

Could tell us new stories about the world:can talk evolution of the universe before the Big Bang(interpreted as a collision of branes)explains facts about black holes, dark matter etc.

But these are promises and prospective undertakingsIoan Muntean String Theory: Explanation and Fundamentalism

More reasons to. . . love ST

It is “science in the making”

It is mathematically fertile and can provide “mathematicalpredictions” (?)

It is open to interpretive questions (?)

As any other QG, it is a fertile middle ground betweenphilosophy (metaphysics and epistemology) and theoreticalphysics

Amendments

String theory does not have the features of a scientific theory

Call it a program/direction of research, not a theory

Interpret it as a collection of mathematical models

1 each model is false and has intentional falsities inserted2 the model does not latch onto the world

string theory does not explains facts, at least not directly.

it may predict mathematical facts or even providemathematical results

Amendments

Interpret it as a collection of mathematical models1 each model is false and has intentional falsities inserted

2 the model does not latch onto the world

Amendments

Interpret it as a collection of mathematical models1 each model is false and has intentional falsities inserted2 the model does not latch onto the world

Amendments

Some reasons not to. . . love it

String theory is a “glorified” QFT (and nothing more)

“a chip of the same block” as QFT has its own skeleton in thecloset

String theory:

is background dependent (Smolin, Rovelli, Penrose)does not seem to address deep philosophical issues (?)never solved or addressed the measurement problem

All known string theories are perturbation theories

String solutions are unstable (?)

String theory:

is background dependent (Smolin, Rovelli, Penrose)

does not seem to address deep philosophical issues (?)never solved or addressed the measurement problem

String theory:

is background dependent (Smolin, Rovelli, Penrose)does not seem to address deep philosophical issues (?)

never solved or addressed the measurement problem

String theory:

A reason to hate it: background dependency

ST presupposes a spacetime background and by this it defiesgeneral relativity (???)

Philosophers do not like this dependency either (SeeIntroduction to ?)

So does QFT, it involves a fixed spacetime geometry (apriori?)

But this is against the very principle of general relativity.

In String Theory geometry is not dynamical anymore.

It is like the “unmoved mover” or the ether.

The prodigal ST

“What is very frustrating is that . . . string theorydoes not seem to fully incorporate the basic lessonof GR, which is that space and time are dynamicalrather than fixed, and relational rather than absolute. . . all that happens is that some strings moveagainst this fixed background and interact with oneanother.” ((?, 159))

Roughly speaking, ST replicates the mistake of Newtonianphysics and overlooks some central achievements of GR.

i.e. it does mesh well with mature/successful/well-acceptedscientific theories.

The prodigal ST

Bleak philosophy of string theory: confirmation andprediction

Is ST confirmed directly?

No, it is not.

Is ST successful in providing novel predictions?

No, it is not.Some predictions are in sight in “string cosmology” or stringyblack holes

I would not apply a “naive falsificationism” to string theory.

No, it is not.

Some predictions are in sight in “string cosmology” or stringyblack holes

No, it is not.

Apply GOF falsificationism to string theory?

No data, no falsification, no science

Hence string theory is closer to:

MathematicsMetaphysicsSpeculationMysticism, new-age cults or even religion (it creates its ownlingo).

Some deemed ST (and QG) as “postmodern physics”(Nambu)

Several physicists aired these worries: L. Smolin, P. Woit, R.Penrose

Mathematics

MetaphysicsSpeculationMysticism, new-age cults or even religion (it creates its ownlingo).

MathematicsMetaphysics

SpeculationMysticism, new-age cults or even religion (it creates its ownlingo).

MathematicsMetaphysicsSpeculation

Mysticism, new-age cults or even religion (it creates its ownlingo).

Experimental agnosticism

Stay agnostic about its direct experimental confirmation

“Test me if you can!”

Credits go tohttp://icanhascheeseburger.com

Less bleak philosophy of string theory: some virtues

What theoretical dimensions of scientific success are known?

1 Unification2 Explanation3 Elegancy, Cohesion, Beauty, Simplicity, you name it. . .4 Problem Solving

1 is obvious and recognized as such (but deserves attention,too)

3 difficult to define, vague, ambiguous

4 is a interesting topic in itself (Ex: string and anomalies)

Here I tackle 2 and relatedly, 1.

Why 2?

What theoretical dimensions of scientific success are known?

1 Unification2 Explanation3 Elegancy, Cohesion, Beauty, Simplicity, you name it. . .4 Problem Solving

Why 2?

What theoretical dimensions of scientific success are known?1 Unification

2 Explanation3 Elegancy, Cohesion, Beauty, Simplicity, you name it. . .4 Problem Solving

Why 2?

What theoretical dimensions of scientific success are known?1 Unification2 Explanation

3 Elegancy, Cohesion, Beauty, Simplicity, you name it. . .4 Problem Solving

Why 2?

What theoretical dimensions of scientific success are known?1 Unification2 Explanation3 Elegancy, Cohesion, Beauty, Simplicity, you name it. . .

4 Problem Solving

Why 2?

What theoretical dimensions of scientific success are known?1 Unification2 Explanation3 Elegancy, Cohesion, Beauty, Simplicity, you name it. . .4 Problem Solving

Why 2?

Does string theory “latch onto reality”? If so, how?

If string explanation is succesful, one can try to run an“inference from the best explanation”.

But this inference needs to be precedeed by an analysis of thesurplus structure of string theory.

2010 11 psa montreal explanation and fundamentalism

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