Limitations to Underdetermination of Theory Building and their Role

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					Limitations to Underdetermination
of Theory Building and their Role in
       Fundamental Physics

            Richard Dawid

   Empirical Confirmation and Fundamental Physics

• In various ways, fundamental physics today has problems to
  connect to empirical testing.
   – Gap between characteristic energy scales and range of experiments.
     (GUTs, SUGRA, Strings...)
   – fundamental conceptual problems, which prevent empirical
     predictions. (Strings in particular)
   – Theoretical scenarios where a large part of the conjectured structure
     seems to be unobservable in principle. (multiverses)
• The situation cannot be expected to change in the
  foreseeable future.

                        The Theories‘ Status
- According to a canonical understanding empirically unconfirmed
  theories are mere hypotheses.

+   Theories do have a stable development and play the role of well
    established theories over decades.
+   A close interdependence between various fields(strings, inflation,
    part. phys. model building) stabilizes the overall system.
+   Physicists working on empirically unconfirmed theories in several
    cases do have substantial trust in their theory‘s viability. (strings,
•   Physicists from other fields and philosophers of science tend to be
    more sceptical.

=> The canonical understanding of theory assessment may not be
   adequate for grasping the status quo of fundamental physics
    Underdetermination of Scientific Theory Building

      by       all possible evidence     availlable evidence


ampliatively   Quine [‚reasons for Sklar, Stanford,
               indet. of transl.‘] Hoyningen-Huene
               van Fraassen        (transient underdet.)
                                   Scientific Underdet.

 The Canonical Understanding of Theory Assessment

• Theory confirmation is based on empirical testing.
• Theoretical reasoning can‘t replace empirical testing because
  of scientific underdetermination.
• Considerations about scientific underdetermination, in
  particular about the likelihood of unconceived alternatives, do
  not play a significant role in determining a theory‘s scientific
   – If we find a theory to be consistently predictively successful, we don‘t
     have to think about possible unconceived alternatives
   – If no empirical confirmation for a theory is found, assessments of
     underdetermination don‘t help either.

  String Theory & Scientific Underdetermination

• String Theory, 35 years after it was first proposed, remains
  theoretically incomplete and empirically unconfirmed.
• Nevertheless, it is highly influential and considered
  trustworthy by its exponents.
? Why?

• Trust in the theory is based on theoretical arguments.
• Claim: Those arguments all amount to
  assertions of limitations to scientific underdetermination.
• Two types of arguments of that kind: external & internal.

            External Arguments for ST’s Viability

Directly implying limitations to ScU:
• Argument of no choice.

Directly against ScU’s significance, indirectly for limit. to it:
• Meta-inductive argument of success of consistency-driven
  theory dynamics in particle physics.
• Surprising explanatory connections which emerge even
  though ST was not devised to produce them.

  All these kinds of argument are known from other scientific fields. They get
  particularly strong in ST, however.

       Internal Arguments for ST’s Viability build on
                    Uniqueness Claims
• Structural Uniqueness :
   further theory succession would be implausible under certain conditions.
    => Final Theory Claim

• Final theory Claims also based on
  - full unification.
  - lower limit to distance scales due to T-duality.

! Int. arg. arise only in ST. As they rely on its validity, they are circular.
! Combined with ext. arg., they strengthen the case for ST’s viability.

   Expecting further theory succession implies an assumption of scientific
   underdetermination. Final theory claims work against it.


• Constructing a consistent theory becomes so difficult that
  successes in that direction carry increasing weight.
• The general format of the scientific process changes:
  succession of limited but fully developed theories ==>
  improving a universal theory without concrete perspective of completion.

 Both developments create an environment that suggests
  strong limitations to scientific underdetermination.
 Assessment of scientific underdetermination plays a more
  central role in theory assessment.

      A Critical Method or Self-Fulfilling Prophesy?

Theories can be questioned and rejected based on theoretical
  theory assessment.
• New theoretical alternatives may be found.
• Consistency problems may arise.
• No theoretical progress for a long time raises the question
  whether the theory has a coherent form.
• Empirical data can serve as an indirect „test“ of the viability of
  assessments of underdetermination.
   – If predictions are confirmed, they strengthen the general case for AoU.
   – If they are refuted, they weaken the general case for it.

    The Status of Empirically Unconfirmed Theories

• Assessment of scientific underdetermination can never fully replace
  empirical confirmation.
• However, it may make sense to take it as a strategy for establishing
  scientific knowledge about the world in the absence of empir. data.
• AoU can establish an intermediate epistemic status for theories that
  lies between „empirically confirmed“ and „pure hypothesis”.
  (Maxwell thought about such an intermediate status for atomism in
  the 1870s)
• A new concept of theory assessment emerges where AoU is one
  important pillar.

! New conception is not based on an outright inconcistency of the old
  one but solely on arguments of plausibility and coherence.

      Underdetermination and Scientific Realism

• Stanford and Hoyningen-Huene: The threat of unconceived
  alternatives implies the rejection of scientific realism.
• If assessments of the likelihood of unconceived alternatives
  are part of science, the philosopher of science may use the
  scientist‘s assessment to retain access to a realist
  interpretation of scientific theories.
• One crucial question: What is the conceptual framework
  within which scientific underdetermination is being assessed
  and how can that framework be legitimated itself?


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