1
Whos afraid of underdetermination? (Not I,
said the Structural Realist)

• John Worrall
• Philosophy, Logic Scientific Method
• London School of Economics

2
Part 1 Laudan and Leplin leave things much as
they were

• 2 main theses
• 1. What they claim There is no general
  guarantee of the possibility of empirically
  equivalent theories (449)
• 1 What the argument if successful - would
  establish any finding of empirical equivalence
  is both contextual and defeasible

3
Part 1 Laudan and Leplin leave things much as
they were

• 2. The empirical equivalence of T and T does not
  entail that the choice between T and T is
  evidentially underdetermined
• One of a number of empirically equivalent
  theories may be uniquely preferable on
  evidentially probative grounds (450)
• AND as a consequence
• The thesis of underdetermination, at least in so
  far as it is founded on presumptions about the
  possibility of empirical equivalence for theories
  .. stands refuted. (466)

4
Part 1 Laudan and Leplin leave things much as
they were

• Argument for thesis 1 (1) uses 3 premises
• (i) VRO the variability of the range of the
  observable
• (ii) NAP the need for auxiliaries in
  prediction
• (iii) IAA the instability of auxiliary
  assumptions

5
Part 1 Laudan and Leplin leave things much as
they were

• First note an important ambiguity in the term
  empirically equivalent (and in their
  definition theories are empirically equivalent
  just in case they have the same class of
  empirical, viz observational, consequences.
  (451)

6
Part 1 Laudan and Leplin leave things much as
they were

• What (i)-(iii) entail is allegedly that
• T and T may be empirically equivalent at one
  stage of science but not at some later stage.
• VRO is a mistake but

7
Part 1 Laudan and Leplin leave things much as
they were

• Use of auxiliaries just seems sloppy
• IF T and T are single isolated theories then
• IF Duhem is right
• (AND he is!)
• THEN T and T are automatically empirically
  equivalent since both have set of empirical
  consequences Ø

8
Part 1 Laudan and Leplin leave things much as
they were

• IF we include all the necessary specific,
  auxiliary, instrumental assumptions to create two
  theoretical frameworks F and F (built around the
  core T and T)
• THEN problem simply re-arises with F and F
• Of course this tie may be broken later by
  addition of a further auxiliary to one or other,
  but the other can then catch up.
• Exactly the Duhem way into underdetermination

9
Part 1 Laudan and Leplin leave things much as
they were

• So there is a general proof of empirical
  equivalence
• Given any finite set of data D and any rival core
  theories T and T we can always engineer the
  auxiliaries so that both F and F entail D.

10
Part 1 Laudan and Leplin leave things much as
they were

• So in fact everything rests on thesis 2- viz
• 2. The empirical equivalence of T and T does not
  entail that the choice between T and T is
  evidentially underdetermined
• One of a number of empirically equivalent
  theories may be uniquely preferable on
  evidentially probative grounds (450)

11
Part 1 Laudan and Leplin leave things much as
they were

• This has to be correct of course
• (as those of us who think that there is a
  solution to the Duhem problem have long banged
  on about)
• Prediction/Accommodation

12
Part 1 Laudan and Leplin leave things much as
they were

• L Ls own arguments somewhat obfuscatory
• A. significant evidential support may be
  provided for a theory by results that are not
  empirical consequences of the theory. (460)
• B. true empirical consequences need lend no
  evidential support to a theory. (ibid)

13
Part 1 Laudan and Leplin leave things much as
they were

• B just rests on a confusion between no support
  and not much support
• A argument 1 next instance
• argument 2 spread of support to rest of a
  theory
• BUT only when theory is unified
• My prediction/ accommodation distinction
  similarly dependent on this sort of judgment
• So back to where we always were

14
Part 2 Underdetermination and Structural Realism
15
Underdetermination and Structural Realism

• But these are merely names of the images which
  we substituted for the real objects which Nature
  will hide for ever from our eyes. The true
  relations between these real objects are the only
  reality we can attain .
• If the relations are known to us, what does it
  matter if we think it convenient to replace one
  image by another
• In fact anything you said about those images
  would be illusory/meaningless
• (Or at best of some heuristic value)

16
Underdetermination and Structural Realism

• Hence (E)SR although our current theories may
  not be true, their basic theoretical terms may
  have no real referent and we cannot, in
  principle, know whether or not they have -,
  nonetheless it is reasonable to believe that they
  are at least approximately structurally
  correct.

17
Underdetermination and Structural Realism

• That is, the structure of our successful theories
  reflects to some extent the real structure of the
  universe.
• And its reasonable to believe this, despite
  scientific revolutions, precisely because
  structure is preserved (or quasi-preserved)
  through revolutionary change.
• And of course because each successive theory has
  enjoyed striking and independent predictive
  success (NMA)

18
Underdetermination and Structural Realism

• SR is clearly committed to the view that the full
  cognitive content of any theory T is captured by
  the Ramsey sentence of T
• And a good job too!

19
Why the only sensible view is the Ramsey view

• First, what is the RT of any given T?
• Ramseys whole approach just like the whole
  underdetermination issue - is based on making a
  distinction between theoretical and observational
  terms.

20
Why the only sensible view is the Ramsey view

• Any scientific theory S will therefore involve a
  number of theoretical predicates T1,, Tn and a
  number of observational predicates O1,,Om
• So we can write S as S (T1,,Tn O1,,Om)

21
Why the only sensible view is the Ramsey view

• Then the Ramsey sentence RT of T is formed by
• (i) replacing all occurrences of any theoretical
  predicate Ti by a variable Ti to form
• S (T1,,Tn O1,,Om) and
• (ii) existentially quantifying on all those
  variables to form
• VT1, ,VTn S (T1,,Tn O1,,Om)

22
Why the only sensible view is the Ramsey view

• So why is it obvious that the full cognitive
  content of any theory T is captured by its RT?
• First and foremost everybody agrees (though then
  forgets it) that standard referential semantics
  is entirely misleading
• At any rate when it comes to theoretical terms
  in science
• You obviously cant stand outside of all
  theory and compare what the theory says with an
  independently given reality

23
Why the only sensible view is the Ramsey view

• Global descriptivism (at least so far as
  theoretical terms are concerned)
• Causal referential talk would be just more
  theory
• Unless you appeal to something mystical (clearly
  unobservable but nonetheless somehow
  apprehendable semantic glue)

24
Why the only sensible view is the Ramsey view

• If asked what does gluon mean? I can only
  rehearse the latest theories involving gluons
• N.B. All of those theories
• (Lots of mistakes made by leaving some theory
  outside (i.e. unRamseyfied))
• That is, a gluon, so far as we can tell, is the
  whatever it is that does this that and the other
  (as stated by those theories)
• But then if you have accepted this, you have
  accepted the Ramsey view

25
Ramseyfication and Underdetermination

• Lots of ways of convincing yourself there is a
  problem with underdetermination that are
  immediately obviated once you accept Ramsey.
• For example
• 1. The natural argument
• 2. Tacking paradox
• 3. Schmelectron theory
• 4. As if

26
Ramseyfication and Underdetermination

• 1. The natural argument
• Take any theory T and take the set O of the
  theorys consequences that are expressible
  entirely in the observation language
• Take any conservative extension of O back into
  the full language
• There are indefinitely many of those
• BUT R(T) is itself expressible in the observation
  language

27
Ramseyfication and Underdetermination

• If we restrict initially to the data set, then
  things are different
• But that takes us back to Duhem and unity

28
Ramseyfication and Underdetermination

• 2. The Tacking paradox
• T GTR God exists has the same set of
  observational consequences as T GTR
• Moreover so does T GTR God exists
• T and T are mutually inconsistent
• You want to say that T and T are only
  nominally different they have no cognitive
  content not already held by T

29
Ramseyfication and Underdetermination

• R(T) R(T) a tautology R(T)
• R(T) R(T) a tautology R(T)
• VFVx (F x) (take F xx)
• V F ?x( F x) (take F (xx))

30
Ramseyfication and Underdetermination

• Take Tcurrent theory of electrons
• T says the same except that you consistently
  substitute schmelectron for electron
• R(T) R(T)

31
Ramseyfication and Underdetermination

• 4. T theory of electrons
• T Everything is as if electrons (as described
  by T) exist
• Always mystified by this T just a
  reformulation of T
• Just a reexpression of the Ramsey sentence
• If you add but actually they dont exist?
• Only sense that can be made is surely
  forward-looking
• But this theory of the future will be a different
  theory with a different Ramsey sentence

32
Ramseyfication and Underdetermination

• Summary
• 1. The Duhem problem can be solved
  satisfactorily hence the main way into alleged
  undetermination is pre-blocked
• (Laudan Leplin only appear to add something to
  this.)
• 2. Several of the other ways in which you might
  think there is a problem of underdetermination
  evaporate once you take the Ramsey view.

33
The Ramsey view and the Newman objection

• Since so many people seem to believe that the
  result shows that SR collapses into anti-realism,
  let me start to try to erode that belief
• 1. Neither Ketland nor Putnam nor Newman has
  proved that SR entails that any two empirically
  equivalent theories, in the normal sense, are
  equally true (or approximately true or, rather,
  approximately reflect an external reality)

34
The Ramsey view and the Newman objection

• 2. Not just a question of getting the data right.
  First the two theories share all the consequences
  expressible in the observational language
• 3. And clearly some of these may be theoretical
  in anyones book e.g. there are unobservables
  (i.e objects with no (directly) observable
  properties) is (a) purely in the observation
  language and (b) clearly theoretical.

35
The Ramsey view and the Newman objection

• 4. Moreover, the theories that SR takes to
  reflect external reality are not only
  (predictively) empirically successful but also
  unified.
• (So SR would claim that Copernican theory
  reflects reality better than Ptolemaic, despite
  their data equivalence (not empirical
  equivalence), because of the greater unity of
  Copernican theory.)

36
The Ramsey view and the Newman objection

• 5. Surely the RT says that the theoretical terms
  exist it characterises them in observational
  terms, or better - in how they interrelate with
  one another and how they structure the phenomena
  but this is patently not to eliminate them.
• (6. Cp Quines famous account of ontological
  commitment)

37
The Ramsey view and the Newman objection

• (7. David Lewis My proposal could be called an
  elimination of theoretical terms, if you must
  for to define them is show how to do without
  them. But it is better called a vindication of
  theoretical terms for to define them is to show
  that there is no good reason to want to do
  without them.)

38
Is Structural Realism really realism?

• Many will be unconvinced if this is really the
  SR that you defend, then for all you say,it isnt
  really realism.
• Danger of quibbling about words call it
  anti-realism if you like
• (there certainly are realisms that it is anti!)
• Doesnt count on either of Putnams definitions
• A. A realist needs to assert that a theory T may
  be false even though its RT is true

39
Is Structural Realism really realism?

• B. A realist asserts that the theoretical terms
  in our current successful theories in mature
  science refer (though she can then allow that
  what those theories say about the entities to
  which they refer is only approximately rather
  than outright true)
• (In fact SR asserts that the mode of reference of
  its terms is just as problematic,
  uncharacterisable as the approximate truth of a
  theory T.)

40
Is Structural Realism really realism?

• So why do I hold that the right judgement is that
  SR is a version of realism?
• What is realism?
• 1. Metaphysical realism the assertion of the
  existence of a reality independent of the human
  mind???
• NO 1. There exists a structured reality of
  which the mind is a part and, far from imposing
  their own order on things, our mental operations
  are simply governed by the fixed laws which
  describe the workings of Nature.

41
Is Structural Realism really realism?

• 2. Methodological realism 1 the structure
  of reality is at least in part intelligible to
  the human mind
• 3. Scientific realism 1 2 successful
  theories the unified theories that explain the
  phenomena without ad hoc assumptions are
  approximately true.

42
Is Structural Realism really realism?

• IF you are wedded to a correspondence or semantic
  view of truth as your account of corresponding
  with reality, then SR does not count.
• But there is no reason why the way in which a
  theory mirrors reality should be the usual
  term-by-term mapping described by traditional
  semantics

43
Is Structural Realism really realism?

• SR takes it that the mathematical structure of a
  theory may globally reflect reality without each
  of its components referring (or being known to
  refer) to a separate item of that reality.
• If you insist on reference for truth (or near
  reference for approximate truth) then SR is not
  realism
• BUT theres no sustainable version of realism
  attainable if you thus insist

44
Is Structural Realism really realism?

• SR takes it that the mathematical structure of a
  theory may globally reflect reality without each
  of its components referring to a separate item of
  that reality.
• If you insist on reference for truth (or near
  reference for approximate truth) then SR is not
  realism
• BUT theres no sustainable version of realism
  attainable if you thus insist
• Structural realism is the only viable position
  (my confusion, following Poincaré)

45
Is Structural Realism really realism?

• Duhem(1906, 28)
• The highest test, therefore, of our holding a
  classification as a natural one is to ask it to
  indicate in advance things which the future alone
  will reveal. And when the experiment is made and
  confirms the predictions obtained from our
  theory, we feel strengthened in our conviction
  that the relations established by our reason
  among abstract notions truly correspond to
  relations among things.
• Thats all it is! Accept it!