Download PoS Week 13

PH201/400 – Week 13
Scientific Explanation III
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Causal Explanation
Most criticisms that have been marshalled
against the DN and the IS models of
explanation have a common focal point:
causality.
Explanation in many cases amounts to
finding the causes. That is, we explain A by
saying what caused A.
Question: What is causality?
 Next week’s lecture.
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Unification and Explanation
Motivation: Famous cases of unification
Case 1: The Newtonian Synthesis.
Prior to Newton we had a miscellaneous collection of laws:
•Kepler’s laws of planetary motion
•Galileo’s laws of falling objects
•Laws of projectile motion
•Laws for the pendulum
•...
Newton showed that all objects were subject to the same
gravitational force law and the same equation of motion. This
made all the individual laws derivable from the same theory.
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Case 2: Maxwell’s Field Theory
Prior to Newton we had a miscellaneous collection of
laws:
•Laws governing electric phenomena
•Laws governing magnetic phenomena
•Optical laws
•…
Maxwell’s ‘electromagnetic’ field theory made all these
laws appear as theorems of one overarching theoretical
framework.
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Crucial features:
•Both cases systematise knowledge by
subsuming previously separate laws under
common theoretical framework.
•These separate laws described phenomena
that belong to different domains (celestial and
terrestrial phenomena; electric, magnetic and
optical phenomena).
So: these theories have ‘unifying power’.
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Leading idea:
• Our comprehension of the universe is
increased as the number independent
assumptions we require decreases.
• Such a unification is explanatory.
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Michael Friedman (1974):
‘I claim that this [unification] is the crucial property
of scientific theories we are looking for; this is the
essence of scientific explanation – science
increases our understanding of the world by
reducing the total number of independent
phenomena that we have to accept as ultimate or
given. A world with fewer independent phenomena
is, other things being equal, more comprehensible
than one with more.’
Hence, unification is explanatory.
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Friedman points out that this is a global
conception of explanation:
‘[…] the kind of understanding provided by
science is global rather than local. Scientific
explanations do not confer intelligibility on
individual phenomena […] However, our overall
understanding of the world is increased; our total
picture of nature is simplified via reduction in the
number of independent phenomena that we
have to accept as ultimate.’
So the programme is to spell out what
unification amounts to.
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Intuition Pump and Agenda Setting
Take Kepler’s three laws (K1, K2, K3) and
Galileo’s law of the free fall (F1).
We achieve a unification if we have other
more general laws from which these laws
follow.
Newton: law of motion (N) and the law of
gravity (G):
N&G  K1
N&G  K3
N&G  K2
N&G  F1
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Condsider an alternative theory U:
U= K1&K2&K3&F1
Obviously:
U  K1
U  K3
U  K2
U  F1
Intuitively, N&G achieves real unification
while U is a spurious unification.
The challenge is to account for this intuition.
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Kitcher’s Theory of Unification
Unification through argument patterns:
‘[...] a theory unifies our beliefs when it provides one
(or more generally, a few) pattern(s) of argument
which can be used in the derivation of a large number
of sentences which we accept.’ (Kitcher)
Unification is achieved if similar arguments
are used in the derivation of many sentences.
But: what is an argument pattern?
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According to Kitcher, an general argument
pattern consists of:
(1) A schematic argument
(2) A set of filling instructions
(3) A classification.
Analogy: Formal logic, which provides
argument patterns (like modus ponens) and
studies their general properties.
But the structures in science are different.
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(1a) Schematic sentences: We obtain a
schematic sentence by replacing some, but
not all non-logical expressions with dummy
letters in a ‘normal’ sentence.
Note: Not all non-logical vocabulary can be
replaced. Why not?
(1b) Schematic argument: a sequence of
schematic sentences.
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(2) Filling instructions: A set of filling
instructions for a schematic sentence is a set
of directions for replacing the dummy letters
in the schematic sentences. That is, it is an
instruction how to ‘load’ the scheme.
(3) Classification: A classification for a
schematic argument is a description of the
inferential characteristics of the schematic
argument. It has to specify which sentences
figure as premises, which ones are derived,
what rules of inference are used, and what
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counts as valid argument.
Example: Newtonian general argument
pattern
Schematic argument:
(i) The force on A is B
(ii) The acceleration of A is C
(iii) Force=mass × acceleration
(iv) (Mass of A) × C = B
(v) D = E
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Filling instructions
•A has to be replaced by an expression
referring to the body under investigation
•B has to be replaced by a function
•C has to be replaced by an expression giving
acceleration of the body as a function of its
co-ordinates and time
•D is the set of co-ordinates describing the
position of the body
•E is a function explicitly depending on time
•
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Classification
• (i)-(ii) have the status of premises
• (iv) is obtained from (i)-(iii) by substitution
of identicals
• (v) follows from (iv) using calculus
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An explanatory theory then is set T of
argument patters so that four conditions are
satisfied.
(α) Coverage:
Let K be the set of all accepted sentences in
a certain domain.
Then T contains at least one pattern for
each member of K.
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(β) Paucity:
The power of T varies inversely with the
number of patterns in the set. The fewer
patterns we need to cover all members of K
the greater the unifying power.
(γ) Similarity:
Similarity among the members the class of
patterns: The more similar the patterns in T,
the greater the unifying power of the set.
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(δ) Stringency:
The patterns in T have stringency.
An argument pattern is has stringency to
the extent that the instantiations of the
pattern resemble each other.
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Example: ‘fatalism pattern’
Schematic sentences:
(i) God wants it to be the case that A.
(ii) What God wants to be the case is the case.
(iii) It is the case that A.
Filling instructions:
Substitute any accepted sentence for A.
Classification:
(iii) Follows from the (i) and (ii) by logic.
This pattern lacks stringency.
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Study question:
How can Kitcher’s unification account of
explanation deal with the problems the DN
model faces?
In particular think about:
-Asymmetry
-Irrelevance
-Accidental generalisations
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Problems and Questions
1.The Role of General Laws
Unification can be achieved on the basis of low
level regularities. But such regularities do not
explain. In order to explain a phenomenon we
need general laws and theories.
Example:
K = All sentences describing the falling of objects.
Argument pattern = Galileo’s laws of the fall
Claim: This is a unification but it fails to explain
because there is no general law in it.
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2. Solitary Patterns
In some cases explanation can be achieved by
patters that are instantiated only once, but
Kitcher’s account would seem to rule out such
cases on grounds of stringency (there is
nothing the instantiation could resemble).
Example:
Hempel’s example with the thermometer (see Weber p. 453)
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Questions:
1.How could Kitcher respond to these
criticisms?
2.If he can’t how damaging are they?
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Rebooting Intuitions
Morrison (2000) argues that the entire
account get started on the wrong foot:
‘Rather than analysing unification as a special
case of explanatory power, as is commonly
done in the literature, I claim that they
frequently have little to do with each other and
in many cases are actually at odds.’
Hence, the association of unification with
explanation is a mistake.
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This is because:
(1) Unification often reveals little, if anything,
about the ‘machinery’ of a particular system.
But it’s the mechanism underlying a system, or
the causal interaction of its parts, that explains
its behaviour.
Example: understanding the propagation of
light involves understanding the mechanism by
which light propagates, not just a specification
of its speed and wavelength. But simple
reference to the laws does not provide that.27
(2) The features of theories that do facilitate
unification are not the one that allow us to
explain them. Unification is often driven by
mathematical rather than physical relations.
An account the unifies phenomena does not
provide a substantive account of the
phenomena themselves.
Critics pointed point out: ‘Newton’s unification
allowed us to calculate everything but
explained nothing.’
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(3) Theoretical unification need not (and often
does not) lead to ontological unification.
Maxwell’s theory offers a unified mathematical
description of the electric and magnetic fields,
but does not provide unified ontological
account. The entities are ‘kept separate’.
But a unified ontology is what would be
explanatory.
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Causation and Unification:
Peaceful Coexistence?
Are causal and unificatory explanations
irreconcilable opposites?
View 1: unificatory explanation is parasitic on
the causal explanation. We explain general
regularities by identifying the causal
mechanisms that produce the events they
cover. So at the end of the day it’s causation
that matters.
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View 2: An opposing tradition claims that
scientific explanation is global rather than
local. Sciences is not interested in questions
about individual events. Causal explanations
of particular occurrences recapitulate the
ordering derived from the systemtization of
regularities.
Are these views reconcilable?
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