Underdetermination:
The Big Picture
Kareem Khalifa
Department of Philosophy
Middlebury College
Overview
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•
•
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What is Underdetermination?
Holistic Underdetermination
Contrastive Underdetermination
Why Underdetermination Matters: Rationality
General Structure of
Underdetermination
Output 1
Output 2
Input 1
Rule/
Process
…
Output n
In words…
• Suppose we have input of type A.
• Furthermore, we have a rule that is consistent
with the following:
– If A, then B, C, D, … or Z.
• Then the input and the rule underdetermine
the outputs.
• Sometimes the “blame” is assigned to the
inputs; sometimes to the rules; sometimes to
both.
Simple (Non-Scientific) Example
10 apples,
0 oranges
Total
Expenditure
on apples
and oranges
= $10
8 apples,
1 orange
Total expenditure
= ($1 x #apples) +
($2 x #oranges)
6 apples,
2 oranges
4 apples,
3 oranges
2 apples,
4 oranges
So your total expenditure (input) plus the price of
fruit (rule) underdetermines the exact quantity of
apples and oranges that you purchase (output).
0 apples,
5 oranges
Scientific Underdetermination:
Basic Structure
Theory 1
Theory 2
Empirical
Evidence
“Scientific
Method”
…
Theory n
Scientific Underdetermination:
Simple Example
Correlation
between
video
games,
violent
behavior
Video games
cause violence
Causal
Inference
Violence
causes video
games
…
Some third
factor causes
both
Five ways of fleshing out
underdetermination
1. Clarify the kinds of evidence that underdetermine (e.g.
correlations, experimental, census, ethnographic, etc.)
2. Clarify the kinds of rules that underdetermine (e.g.
significance tests, crucial experiments, Mill’s Methods,
etc.)
3. Clarify the kinds of hypotheses/theories that are
underdetermined (causal hypotheses, those concerning
unobservables, qualitative, etc.)
4. Determine the strength of the underdetermination
a.
b.
Nonuniqueness: more than one hypothesis is acceptable
Egalitarian: any hypothesis is acceptable
5. Clarify if the underdetermination is transient or
permanent.
Two Kinds of Underdetermination
• Holist Underdetermination (HU):
– Input: evidence
– Rules: Best fit/coherence
– Output: theories to accept, rules
• Contrastive Underdetermination (CU)
– Input: evidence and hypotheses available
at a given time
– Rules: any that identify which available
hypothesis “best fits” the evidence
– Output: hypotheses to accept (available
and unavailable)
Holist Underdetermination
1. If evidence E disconfirms hypothesis H, then
auxiliary hypotheses A1, …, An must be assumed.
2. If A1, …, An must be assumed, then E does not
contradict H alone, but contradicts the
conjunction of H & A1 & … & An.
3. So, if E is true, then either H is false OR A1 is
false OR … OR An is false.
4. So any disconfirming evidence underdetermines
the hypothesis (auxiliary or otherwise) to be
rejected.
Comparison of
Standard View and HU
Theory:
Aux. Hyp: Concrete
apparatus is
measuring an F.
All F’s are G’s
Aux. Hyp.: Concrete
apparatus is measuring a
not-G
Falsifying Experiment:
This F is not a G
Aux. Hyp.: Scientist did not
make a mistake.
HU
Which hypothesis do we reject?
Aux. Hyp.: Concrete
apparatus is not
malfunctioning
Standard
View
Contrastive underdetermination
1. Suppose that, at time t, H is the available
hypothesis that “fits” best with the evidence E.
2. Throughout the history of science, there has
always been a hypothesis H* that is unavailable
at t (but available at t+1) that would have fit E at
least as well as H had it been available at t.
3. So at any given time, the evidence
underdetermines the hypothesis that best fits
with it.
HU without CU
• Suppose, contra CU, that there is only one
conjunction of hypotheses H & A1 & … & An
that could possibly fit with the evidence.
• However, HU could still apply: if there is a
contradiction then should we reject H or A1
or…?
CU Without HU
• Conversely, suppose, contra HU, that we knew
that A1 & … & An should be accepted and H
should be rejected.
• However, CU could still apply: is there a
currently-unavailable alternative to H, H*, that
better fits the evidence?
Why Underdetermination Matters
1. A sufficiently strong form of underdetermination
implies that non-rational factors always play a
role in how scientists accept theories.
2. But if scientists are (semi-)irrational in how they
accept theories, then few beliefs are (fully)
rational.
3. So sufficiently strong form of
underdetermination implies few beliefs are
(fully) rational.
Does Underdetermination Imply
Irrationality?
1. If evidence and the rules of scientific method
underdetermine the theory to be accepted,
then something else (call it X) needs to be
added to “pick up the slack” or “cover the
difference.”
2. Evidence + scientific method exhaust the
rational bases of theory acceptance.
3. So X must be a non-rational basis of theory
acceptance.
Recap
• Underdetermination occurs when inputs and
rules fail to provide a unique output.
• In science, the paradigmatic case is when
evidence and the rules of scientific method fail to
provide a unique “best theory” to accept.
• There are many ways of refining this basic idea,
though HU and CU have been the most
prominent.
• Certain forms of underdetermination suggest that
science is not as rational as it appears.