Resisting the pessimistic induction

Psillos

Table of content Introduction Convergent realism Pessimistic induction Psillos's aim Psillos's argument

1. First step

2. Second step

3. Third step

Questions

Introduction

Kuhnian concepts:

1) Scientific revolution

2) Normal science

3) Pre-revolutionary; post-evolutionary theories

Introduction

Two main views:

1. Continuist/retainist account (realist): some parts of pre-revolutionaty theory are retained bt post-revolutionary theory

2. Discontinuist/non-retainist account (Laudan): No parts of the pre-revolutionary theory are retained by post-revolutionary theory

Convergent realism according to Laudan

(R1) The more recent a theory is, the more approximately true it is ->explains -> (S) the success of T

(R2) All terms of a theory genuinely refer->(explains) -> (S) success of T

(S)

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R1 and R2

Pessimistic induction against convergent realism (Psillos)

i. If a past theory T1 was consired approximately true because of its success,

ii. (A) a present theory T2 is considered approximately true becasue of its success

iii. And if T1 and T2 do not share anything (entities, structures, laws*)

iv. Then truth-likeness cannot be explained with the success of theory T

Psillos’s aim

• Reducing Laudan’s list of past successful theories that turned to be false.

Psillos’s argument

Three steps:

1. He rules out all Laudan’s examples, except two, defining “success” and “mature science”

2. He propose the divide et impera move

3. He applies it to rule out these two problematic examples of Laudan's list: caloric theory of heat and dynamical optical ether theories

First step

(a) Definition of success

(b) Definition of mature science

(a) Definition of success

• A T is successful not just if T’s predictions are confirmed and the theory T has been of a broad explanaory scope.

• But also a T must accommodate all facts (known and unknown) in a novel way (that is, in a non ad hoc way)

Novel accommodation

A prediction P of a phenomenon E is use-novel with respect to a theory T if E is known before T is proposed and T does not satisfy

the following ad hoc conditions:

Ad hoc conditions of T with respect E

A body of background knowledge entails the existence of E and

1. Information about E is used in the construction of T; T accommodates E.

2. A theory T is modified into theory T' only because T' predicts E without adding other theoretical or empirical contents

(b) Definition of mature science

A science is mature if:

•All the theories (even in disagreement) share common background believes

•One of this believes is that science has a limited scope of inquire

Problem: (a) and (b) are not enough!

“The present move is not enough to defeat the ‘pessimistic induction’: for it does not account for the fact that at least some past theories which pass both realist tests of maturity and success are nevertheless considered false.” (Psillos, 103)

Second step: The divide et impera move

Psillos wants to reject the non-retentionist premise of the pessimistic induction:

iii “T1 and T2 do not share anything (entities, structures, laws*)”

He argues for a retentionist claim

The retentionist claim

• Something (H) is retained from T1 to T2

• (H) is responsible for the success of T1 and T2

• (H) is (logically?) independent from the rest of the theory. So, H cannot be replaced in T1 by H* and still predict the same facts (that is, without loss in the derivation of a prediction)

Possible candidates for H:

(a) The structure of laws (Worral)

(b) The existence of the entities that the theoretical terms refer to

(c) Theoretical claims and laws (Psillos*)

“.. the genuine empirical success of a theory does make it reasonable to believe that the theory has truth-like constituent theoretical claims. Moreover, if the theoretical constituents that were responsible for the empirical successes of past theories have been retained in subsequent theories, then this gives us reason to be more optimistic about their truth-likeness.” (Psillos, p.104)

Kitcher's and Psillos's account of the components of theories

1) Idle/non-essential component = not indispensable for the success of a theory

2) Essential component = fundamental for the success of a theory

The divide et impera move requirements

•Identify T's essential components, that is, the components responsible for the success of T

•Test that these components have been, are and will be retained in every successful theory in the same mature science

How to distinguish this parts? (I): A rejected solution

According to Psillos, Kitcher does not provide any objective method for this distinction. Kitcher just suggest that we can distinguish between the idle and essential part from the present: what was essential in past theories (and retained from the past theory to the present theory), it will be retained in future theories.

Problem: this is cheating from the future.

Psillos' challenge:

Can a realist, independently from the history of science (a priori), identify essential components and then shows that they are linked with truth-likeness?

How to distinguish these parts?(II): Psillos's solution

As scientists are those who work and make the predictions of theories, they know better than anyone else which components of a theory are the responsible for the success of a theory.

Consequently, they treat with suspicion the components which are not responsible for the success of the theory and uphold the ones that do so.

Third step: rule out the two problematic examples

(a) Caloric theory of heat

(b) Dynamic optical ether

(a) Caloric theory of heat

The cause of the heat as a material fluid was not responsible of the success of the theory

It was logically independent of the components H which really were the responsible of the success

It was worse supported by the empirical evidence than the H

(a) Caloric theory of heat (I)

According to Psillos, if these three conditions are satisfied, then H is retained and approxmately true.

(b) Dynamical optical ether: conservation of energy

Since in the theory of the dynamical optical ether, the principle of conservation of energy, satisfy the three condition listed above, it can be considered as H (as a retained and true part of the theory).

(b) Dynamical optical ether: Does “ether” refer?

“... the term ‘ether’ has been seen as an exemplar of a non-referring scientific term. Does it, then, follow that the whole range of dynamical theories of optics in which ether had a central function cannot possibly be approximately true? Discussion of that issue is postponed until Chapter 12 , where attention turns to theories of the reference of theoretical terms. There I motivate a causal-descriptive theory of reference and defend the view that it is plausible to think of ‘luminiferous ether’ as referring to the electromagnetic field.” (Psillos p.109)

Questions

1. Do scientists always make the distinction between idle and essential component of theory?

1. If it is so, do they have to be always right?

2. What are, according to Psillos, the elements that are retained: theoretical laws or entities; or both? (he speaks about theoretical components)

Questions

3. Is he divide et impera move of Psillos (Kritcher, ¿Worral and Chakravartty?) at odds with holism?

The point is that Psillos claims that empirical evidence only suports (or falsify) one part of the theory but not all (because this part H is the responsable for the success of T)