Anti-realism: The argument from Underdetermination

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Anti-realism The argument from Underdetermination

• The point about atoms and the like is that
  they are purely theoretical. For all we know
  there could be quite different things causing
  what we see (Ladyman, 160)

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Anti-realism

1. To understand anti-realism, we need to contrast
   it with scientific realism. What is scientific
   realism?
2. Argument for anti-realism underdetermination
3. What is underdetermination?
4. Different arguments from underdetermination
5. Some realist responses

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What is scientific realism?

• Scientific realism is committed to taking what
  scientific statements say literally
• For scientific realists, what is the status of
  the observable/unobservable distinction?
• Theoretical terms refer to unobservable entities,
  and statements involving them are assertoric

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Requirements of scientific realism (158)

• Metaphysical requirement
• Entities or kinds of entities talked about S
  exist
• Existence of entities is independent of our
  knowledge and minds
• Semantic requirement
• Statements about S are irreducible and are
  genuinely assertoric
• Truth conditions for statements of S are
  objective and determine the truth or falsity of
  those statements depending on how things are in
  the world.

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Requirements of scientific realism

• Epistemic requirement
• Truths about S are knowable and we do in fact
  know some of them, hence the terms of S
  successfully refer to things in the world
• If you were a realist about the leprechaun
  subatomic theory, then what would you be
  committed to?
• Leprechauns exist mind-independently
• Statements about leprechauns are about subatomic
  particles
• These statements are true/false depending on the
  way the world is
• Truths about leprechauns are knowable.

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Why anti-realism?

• The argument from underdetermination
• What is underdetermination?
• data underdetermine the correct theory when the
  data are insufficient to determine which of
  several theories is true (162).
• That is, more than one explanation is compatible
  with the evidence

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Underdetermination

• Examples curve-fitting Ptolemaic vs. Copernican
  astronomy
• How to decide in cases of underdetermination?
• Context and interest of investigator. Decision
  making sometimes involve contextual (or
  extra-logical) considerations

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Underdetermination

• In cases of underdetermination, would the settled
  on theory or explanation be necessarily the
  correct answer?
• Suppose the theory employs theoretical terms, do
  those terms literally refer to unobservable
  entities?
• What is the implication of underdetermination for
  scientific realism?

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Weak form of underdetermination

• All the data we have gathered are consistent
  with more than one theory, we ought to suspend
  judgment as to which theory is true (Ladyman
  165)
• For any theory T there is always another theory
  T such that
• 1) T T are weakly empirically equivalent
  (both are compatible with the data gathered so
  far)
• 2) If T T are weakly empirically equivalent,
  then there is no way to believe T and not T
• Therefore, there is no reason to believe T and
  not T

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Realist response

• The above argument is valid, but is it sound?
• Does the mere existence of a rival theory
  consistent with the data gathered so far mean
  there is no reason to believe T rather than T?
• E.g. If T is highly corroborated (predictive
  success), and T is introduced ad hoc in the
  sense that T can accommodate all the evidence
  but does not generate any new predictions itself,
  then which should we believe T or T?

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Realist response

• The weak form of the underdetermination argument
  is similar to the problem of induction Every
  observation thus far is consistent with the claim
  that the next observation will be very different
• The response to the weak form of
  underdetermination suggests that one way to
  answer the problem of induction is to say that
  the mere fact that everything observed so far is
  consistent with things being other wise does not
  mean we have no reason to believe that things
  will be very different the next time.

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Duhem-Quine problem and underdetermination

• Recall the Duhem-Quine problem
• 1) If (Theory Background Assumption), then
  Prediction
• 2) Prediction
• Therefore, (Theory Background Assumption)
• Theory or Background Assumption (or both)
• How do we decide which to reject?

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Duhem-Quine problem and underdetermination

• Duhems solution scientists good sense will
  pinpoint the source of the problem (170)
• Duhem does not elaborate on the principles upon
  which good sense rests. The idea is that the
  evolving practice of science solves the problem
  of underdetermination
• Quine holds, in practice, we rely on pragmatic
  considerations to solve the problem. We would
  consider other possibilities before changing the
  laws of logic. It would be impractical to abandon
  the laws of logic.

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Strong form of underdetermination

• How do we tell that we are not dreaming at this
  moment?
• Some dream states are so vivid that during the
  dream you cannot distinguish it from wakeful
  states
• We think we know p
• If we know p then we must know that q is false
• We cant know that q is false
• Therefore, we dont know p.
• That is, there is in principle no way for us to
  decide between p and q

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Strong form of underdetermination

• The dream hypothesis illustrates the stronger
  form of the underdetermination argument The
  strong form says that T and T have the same
  empirical consequences, not just for what we have
  observed so far, but also for any possible
  observations we could make (174). Consider the
  following
• Everything that happens is a result of random
  physical forces
• Everything that happens is designed by God
• Everything that happens is an effect of a prior
  cause

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Strong form of underdetermination (174)

• For every theory there exist an infinite number
  of strongly empirically equivalent but
  incompatible rival theories
• If two theories are strongly empirically
  equivalent then they are evidentially equivalent
• No evidence can ever support a unique theory more
  than its strongly empirically equivalent rivals
• Therefore, theory-choice is radically
  underdetermnined.

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Realist responses

• The first premise of the argument in the previous
  slide is incoherent
• The first premise is false
• Empirical equivalence does not imply evidential
  equivalence
• Well consider the realist responses to the first
  premise of the argument today.

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The first premise is incoherent

• Empirical equivalence requires it to be possible
  to point clearly to the observable consequences
  of a theory. However there is no non-arbitrary
  distinction between observables and unobservables
• The main point of this challenge there is a
  continuum between clear cut cases of observables
  (a tree) and unobservables (a quark)
• So what would count as an instance of empirical
  equivalence?

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Anti-realist rejoinder

• Accept the claim that the term observable is
  vague.
• Vague means a concept has borderline cases that
  neither clearly do nor clearly do not fall under
  the concept.
• However, vague concepts are perfectly usable and
  can be used in making real distinctions
• Consider bald. It is a vague concept. Yet it
  can be used to make distinctions. So vague
  concepts can do epistemological work.

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Second objection to the first premise of the
strong form of underdetermination

• Second attempt the observable/non-observable
  distinction changes with time (176). So whether
  or not two theories are empirically equivalent
  will change with time
• The anti-realist will not be bothered by this
  challenge because the gist is that the
  distinction is relative with respect to time. But
  this just means that at any given time, theory
  choice would still be underdetermined

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How about this realist response?

• Are there real examples of theories that are
  strongly empirically equivalent?
• If they were to exist, then there should be
  constant debates or disagreements between
  scientists. But this is not what we find
  historically.
• How would the anti-realist respond?
• This just shows that theory choice have been
  made. The question is, are there principled ways
  of distinguishing multiple explanations of the
  data?

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Other responses to the strong form of
underdetermination

• We will look at the other responses to the strong
  form of underdetermination on Thursday