bangu _fiction and explanation.pdf

8/19/2019 Bangu _Fiction and Explanation.pdf

http://slidepdf.com/reader/full/bangu-fiction-and-explanationpdf 1/49

Explanatory Fictions

and

Fictional Explanations

Sorin Bangu

Univ. of [email protected]

mailto:[email protected]

mailto:[email protected]



Can fictions explain?

- question of perennial interest

“one of the main and most controversial roles

that fictional assumptions may play” (Suarez 2009, 7)

Fictionalism

- Vaihinger 1920s

- Van Fraassen 1980s (phil of math: H. Field 1980s)

- A. Fine 1990s

- M. Suarez 2000s: 2009 Bokulich, Elgin, Winsberg, Morrison, etc.:

scientists seem fine with a ‘yes’ answer

2




- question of perennial interest

“one of the main and most controversial roles

that fictional assumptions may play” (Suarez 2009, 7)

Fictionalism

- Vaihinger 1920s

- Van Fraassen 1980s (phil of math: H. Field 1980s)

- A. Fine 1990s

- M. Suarez 2000s: 2009 Bokulich, Elgin, Winsberg, Morrison, etc.:

scientists seem fine with a ‘yes’ answer

3




• No: Vaihinger [Hempel, Salmon,…]

• Yes: Bokulich, Elgin… [2009]

Cautious ‘yes’: in what circumstances (new)

Account: two steps

1. fictional explanations2. fictional explanations ≈ (genuine) explanations

fictions fictional explanations (genuine) explanations

role in should be accepted as

2nd part: case study; phase transitions inthermodynamics and SM

4



Can fictions explain? No

5




If SC doesn’t exist, then how is it that there are giftsunder the three?

Explanation :: Understanding

6




If vortices don’t exist, then how is it that the Moonmoves?


7



Can fictions explain? No.

Because falsehoods don’t explain!

If the EXPLANANS are false / fictions, then how is itthat the EXPLANANDUM holds / is true?


8







total falsehoods: gross ‘cancellation effect’

Russell syllogism

bread is stone / milk

stone / milk is nourishing

bread is nourishing

9







idealizations / approximationspartial falsehoods: subtle ‘cancellation effect’

Scientific modeling

false / idealized explanans

true explanandum


Russell syllogism



bread is nourishing

10








Scientific modeling


true explanandum


Russell syllogism



bread is nourishing

11








Scientific modeling


true explanandum


Russell syllogism



bread is nourishing

‘Concerned’ v. ‘unconcerned’ with the truth

[Winsberg 2009]

12








Scientific modeling


true explanandum


Russell syllogism



bread is nourishing

Hempel: no explanation

Salmon: no explanation

‘Concerned’ v. ‘unconcerned’ with the truth

[Winsberg 2009]

13





Hempel

Explananas (L + IC)

Explanandum

Four conditions for anexplanation

…

2. “empirical condition of

adequacy” = the sentencesconstituting the explanans mustbe true (1965, 248)

…

Salmon

• Fictional entities and

fictional processes do not

meet the requirements ofgenuine physical processes

capable of transmitting a

mark.

• fiction F cannot be the

cause of some phenomenon

P—and hence explain P—if

F does not exist.

14





Hempel

Explananas (L + IC)

Explanandum

Four conditions for anexplanation

…

2. “empirical condition of

adequacy” = the sentencesconstituting the explanans mustbe true (1965, 248)

…

Salmon

• Fictional entities and

fictional processes do not

meet the requirements ofgenuine physical processes

capable of transmitting a

mark.

• fiction F cannot be the

cause of some phenomenon

P—and hence explain P—if

F does not exist.

Woodward, Strevens, etc. 15





H. Vaihinger

(1924). The philosophy of ‘as if’ (C. K. Ogden, Trans.).London: Kegan Paul. (Original work published 1911)

Explanation involving fictions Understanding

• “…the fiction induces only an illusion of

understanding” (p. xv)• “[F]iction (…) does not create real knowledge” (p. 88)

16



A diagnostic

The Main Problem

true explananda

false / fictional explanans

17



A diagnostic

The Main Problem

true explananda

false / fictional explanans

Solution:

Fictional content is

eliminable

dispensable, etc.

18



A role for fictions in explanation

Key-question:can fictions explain?

why / when do scientists accept explanations in which the

fictional content of the explanans is (seems) ineliminable?

starting point: the explanandum has fictional content too

- this situation manifests in a variety of ways- not always explicit

- some clear example later

19




Key-question:can fictions explain?

why / when do scientists accept explanations in which the

fictional content of the explanans is (seems) ineliminable?

starting point: the explanandum has fictional content too

- this situation manifests in a variety of ways- not always explicit

- a clear example in 2nd part

20




• indirect, two steps

1. Fictional explanation

2. (Good) fictional explanation genuine explanation

Fictional explanation

21




Fictional explanations

• Cases when both the explanans and the explananda involve fictions

explananda too involve fictions

Explananda = ? ‘Phenomena’ – the Woodward & Bogen sense

Data v. phenomena

- ‘constructed’ out of measurement data -’shaped’ into such as to be invariant

phenomena - not out there, but posited ‘fictional’

Bogen, J., and J. Woodward (1988)Saving the phenomena The Philosophical Review 97: 303-352.

22




Fictional explanations

• Cases when both the explanans and the explananda involve fictions

explananda too involve fictions

Explananda = ? ‘Phenomena’ – the Woodward & Bogen sense

Data v. phenomena

- ‘constructed’ out of measurement data -’shaped’ into such as to be invariant

phenomena - not out there, but posited ‘fictional’

Bogen, J., and J. Woodward (1988)Saving the phenomena The Philosophical Review 97: 303-352.

Data

‘Shaped’ into

phenomena

Phenomena

‘Constructed’ from data (such as to be invariant)

Not out there, but posited

“phenomena (…) cannot be reported by

observational claims.” (p. 343, 306).

Fictions (concerned with the truth)

23




Key-question

why / when do scientistsaccept explanations inwhich the fictional content

of the explanans seems (is)ineliminable?

A:

- When the explananda are‘phenomena’ = also haveineliminable fictional

content.- So not a worrisome caseof [false true]

Fictionalist principle

‘fictions in the explanandaallow fictions in theexplanans’

24




Key-question

why / when do scientistsaccept explanations inwhich the fictional content

of the explanans seems (is)ineliminable?

A:

- When the explananda are‘phenomena’ = also haveineliminable fictional

content.- So not a worrisome caseof [false true]


‘fictions in the explanandaallow fictions in theexplanans’

Monopoly principle

‘buy fictional property with

fictional money’

25




true explananda[phenomena]

fictional/false explanans

26




fictional/false explananda[‘phenomena’]




27






fictionalexplanation



28







acceptable when no genuine

explanation exists = one in which the

explananda are phenomena, not

‘phenomena’


‘fictions in explananda allow

fictions in the explanans’



29



Example of fictional explanation

• Why does water boil?

30



Explanandum

= ‘undergoing a phase transition’

the property of ‘changing state’: liquid vapor (gas)

ice (solid)

- water’s capacity to undergo a ‘phase transition’

- water’s capacity to ‘cross coexistence line’

2. Find realizers + theory

Water (H20) molecules

Statistical Mechanics (QSM)

“When all of this is in, we are entitled to the claim that [boiling] has been

reduced to the [behavior of molecules].”

31



Explanandum



ice (solid)








32

“So, here is a problem for the theoreticalphysicist: prove that as you raise or lower the

temperature of water you have phase transitions to

water vapor or to ice. Now, that’s a tall order!

We are far from having such a proof. In fact

there is not a single type of atom or molecule for

which we can mathematically prove that it will

crystallize at low temperature. These problems are

just too hard for us.”

(D. Ruelle 1991: 123-4)



Explanandum



ice (solid)








33



Explanandum = ‘undergoing a

phase transition’

1. Functionalize

- Water’s capacity to undergo a phase transition = cross ‘coexistence line’

More precisely:

- Define a quantity called ‘free energy’: G = H – TS

- Crossing takes place if G behaves in a certain way = its derivative (tangent)varies discontinuously (Zemansky 1968, 347)

34

H

= enthalpy of the

system = total energy= internal energy + pV



Explanandum


1. Functionalize


More precisely:


- Crossing takes place if G behaves in a certain way = its derivative (tangent)varies discontinuously (Zemansky 1968, 347)

35

H

= enthalpy of the

system = total energy= internal energy + pV

T

= temperature

of the system

S

= entropy of the system

= system's ability to dowork



Explanandum


1. Functionalize


More precisely:


- Crossing iff G behaves in a certain way =

its derivative (tangent) varies discontinuously (Zemansky 1968, 347)

36

-‘singularity’

-‘kink’ -‘sharp corner’

(Stanley 1971, 31)




phase transition’

1. Functionalize

- phase transition = cross ‘coexistence line’ = G has a singularity (kink)

Explanans: water molecules + Statistical Mechanics (QSM)






37




phase transition’

1. Functionalize



2. Find realizers + theory Water (H20) molecules




38

)ln

(ln1

V

Z

V Z G

r

E r e Z




phase transition’

1. Functionalize








39

)ln

(ln1

V

Z

V Z G

r

E r e Z

G can’t have a singularity!

Impossible to find one in principle(mathematical result)

Reduction is blocked at step 2: realizers +

theory

Boiling = case of emergence not

captured in the Kim-Chalmers model

-Not weak emergence

-Not strong emergence due to failure at

step 1




phase transition’

1. Functionalize








40

)ln

(ln1

V

Z

V Z G

r

E r e Z



G depends on Z, so if G is to have

singularities, Z has to have singularities.

But Z can’t have singularities (isanalytic). Z is a finite sum of analytic

functions (not having singularities), and

any finite sum of analytic functions is

analytic (no singularities) So G can’t have

singularities b.c. of Z.




phase transition’

1. Functionalize








41

)ln

(ln1

V

Z

V Z G

r

E r e Z



G depends on Z, so if G is to have

singularities, Z has to have singularities.

But Z can’t have singularities (isanalytic). Z is a finite sum of analytic

functions (not having singularities), and

any finite sum of analytic functions is

analytic (no singularities) So G can’t have

singularities b.c. of Z (Kadanoff 2000)

“So, here is a problem for the theoreticalphysicist: prove that as you raise or lower the

temperature of water you have phase transitions to

water vapor or to ice. Now, that’s a tall order!

We are far from having such a proof. In fact

there is not a single type of atom or molecule for

which we can mathematically prove that it will

crystallize at low temperature. These problems are

just too hard for us.”

(D. Ruelle 1991: 123-4)



• Proof (!): Yang & Lee 1952, etc.)

•singularity problem

A phase transition = singularity in G

can be derived within QSM

if the system contains an infinite

number of particles

N infinite

N / V finite

(‘thermodynamic limit’)

42

N = number of molecules

V = volume

“The existence of a phase transition requires an

infinite system. No phase transitions occur in

systems with a finite number of degrees of

freedom.” (Kadanoff 2000, 238)

Explanandum

Explanans



• ‘Solution’ (Yang & Lee 1952, etc.)





number of particles

N infinite

N / V fin

(taking the ‘thermodynamic limit’)

43

“The existence of phase transitions shows that we have to

be careful when we adopt a reductionist approach. Phase

transitions correspond to emerging properties.”

(Prigogine 1997, 45)

A case of fictional explanation The explanandum has fictional content...

The explanans have fictional content-“no experiments, no matter how finely tuned, can ever determine

whether the ‘corners’ which bound [phase transitions] regions are

sharp or round” (Liu 2001, 328)

- “the transition is neither ‘smooth’ nor ‘singular’” (Liu 1999, 103).

-[singularities are] “artifacts”; “fictions”; “do not exist in reality”

(Liu 1999, S104)

- “the role of a singularity is to represent a phase change

phenomenon. Note that the term ‘phenomenon’ is used here in

the specific sense of Bogen and Woodward. “ (Bangu 2009, 49)

Explanandum

Explanans








number of particles

N infinite

N / V fin


44





A case of fictional explanation The explanandum has fictional content too






(Liu 1999, S104)




Explanandum

Explanans








number of particles

N infinite

N / V fin


45











(Liu 1999, S104)




Explanandum

Explanans








number of particles

N infinite

N / V fin


46









- “the transition is neither ‘smooth’ nor ‘singular’” (Liu 1999, 103)


(Liu 1999, S104)




Explanandum

Explanans



Wrapping up:

how/when fictions can be explanatoryfictional/false explananda

[‘phenomena’]






‘phenomena’




47



Wrapping up:

how/when fictions can be explanatory

singularity: fictional

infinite system: fictional

fictional/false explananda

[‘phenomena’]






‘phenomena’

no explanation exists in which the

explanandum = phase transition (a

real process!) is not represented as

a singularity (and the explanans

don’t involve an infinite system)




48



Thank you

bangu _fiction and explanation.pdf

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