University of Oxford Department of Politics
Philosophy of the Social Sciences: Lectures
Elizabeth Frazer
Michaelmas 2002
Lecture 4: EXPLANATION
II –
the realist
critique of causal explanation
The Problem
Philosophers have had the utmost difficulty in arriving at an operationalisable philosophical analysis of the difference between a genuine ‘cause’ and an ‘accidentally true generalisation’ or simple empirical association. Yet in social science we need to know whether one factor really is the cause of another.
Key Terms
Entailment
In
contemporary logic texts often represented by:
|=
A
logical relationship between statements or propositions. An argument entails its conclusion when the
conclusion follows deductively/necessarily/logically from the premisses. Sometimes expressed as ‘therefore’. The (syllogistic) argument:
P1: All X are Y
P2: All Y are W
P3: No Y are Z
C: All X are W and No X is Z
is
one in which the conclusion is entailed by the premisses
Implication
In
contemporary logic texts often represented by:
|-
A
logical relationship between statements or propositions. An argument implies its conclusion when the
conclusion can be said to ‘follow’ by inductive inference from the
premisses.
P1: All the swans so far
observed are/have been white
P2: It is 1603 and the Queen
is dead
C: The next swan we see will
be white
P: Marriages like Cindy’s
very rarely last
C: Cindy’s marriage will not
last
Necessity
There
is a form of necessity that governs relations between statements (a logical operator);
usually represented by ‘ٱ’ (called ‘box’):
ٱX
(say ‘necessarily X’) is true in any world upon interpretation i iff
[say ‘if and only if’] for every
possible world in the set of all possible worlds, X is true in every possible
world upon interpretation i.
Possibility
A
logical relationship between statements or propositions, usually represented
by ◊ (called ‘diamond’)
◊X (say ‘possibly X’)
Note
that this is equivalent to:
¬ ٱ¬X
Association
Hume was a key figure in
‘associationism’ – an eighteenth century analysis also associated with the work
of John Locke (1632-1704) and James
Mill (1773-1836). The starting
point is the striking way our ideas (mental images etc) are associated with but
independent of sense experiences, and
the way our ideas seem to be systematically associated with each other. Associative laws for long dominated
the philosophical analysis of psychology, and also generated the beginnings of
experimental psychology. It became, in
Lakatos’s words, though, a ‘degenerating research programme’.
From
our point of view the significance of association is that the relationship between the
two entities associated is nothing more than co-occurrence or correlation –
the concept of association carries no connotation or denotation of there being
any mechanical connection or any causal connection, between the two entities.
Cause
1. Hume analyses our idea of cause as having three
distinct elements:
C causes (C->) E if E
follows C; E and C are contiguous or
connected by a chain of contiguous events, and
there is some necessity in the relationship between the two.
Hume
offers two analyses of cause, implying that they are alternative formulations
of the same relation.
‘we may define a cause to be
an object, followed by another , and where all the objects similar to the first
are followed by objects similar to the second.
Or in other words where, if the first object had not been, the second
never had existed.’ (Enquiry Concerning Human Understanding p76)
Note
that the two propositions are not equivalent.
P1. C ^ E
P2. All C (C ^ E)
P3. (¬C) ^ (¬E); or
(¬C) → (¬E)
2. The issue for Hume is whether
our idea of cause has any rational justification. His argument is that
C, ¬E
– not just because, say, a lower branch
supports the cradle in the stead of the one that breaks; but because there is
no logical contradiction in the ‘laws of gravity’ reversing themselves. (cf
EARLIER discussion of Hume on induction)
Hume’s
argument then
·
denies
the rationality of our belief in any necessary connection between those
events in the world we consider to be causally connected.
·
but,
that our belief is not rationally based is not a denial that we do have such a
belief – its foundation is psychological (as is the foundation of our
use of inductive inference, belief in the continuity of past into future etc.)
Hume
anticipates a good deal of Mill’s analysis of
methods for establishing that relations between objects, events or
phenomena are causal. In the Treatise
Hume offers ‘Rules by which to judge of cause and effect’ which anticipate
Mill’s methods of agreement, difference, and concomitant variation. But these ‘rules’ pertain to our minds –
they address the question ‘when do we believe that two events are causally
connected?’
3. Hence the shift to logic.
(Psychology is not an adequate foundation for scientific knowledge)
4. However, the philosophical analysis
of cause runs into the difficulty of the ‘truth value’ of
‘counterfactuals’.
Example
we have a number of
·
background conditions: Oxygen
present, atmosphere dry, ...
and an infinite number of
·
counterfactual conditions: there was no gale blowing, no human being present blowing against the
spark, no fireman directing a firehose at the spark, ...
5. As if that’s not enough the
analysis of cause then runs into a number of difficulties about
[These
issues will be taken up in the next
lecture.]
6. More recently a number of
philosophers have attempted to analyse cause in a way that is realist
about causal connections. One strategy
has been to avoid analysis in terms of ‘events’ (which are discrete) and shift
to analysis of processes which are non-discrete. This may be thought to elide the gap between
C and E into which Hume’s scepticism
gets its hook.
1) C: the brick hitting the
glass, E: the window breaking;
2) C: the matchead striking
the rough surface, E: the spark occurring;
3) C: the branch breaking,
E: the cradle falling
4) C: the sugar dissolving
in the water; E: the syrup forming
Perhaps
the world is more like four than it is like one to three.
Or, can we reconceptualise 1-3 as like 4:
4) the sugar dissolving in
the water is the syrup forming;
5) the water temperature
falling to zero and below is the ice forming. ??
Realism
In
the context of the philosophy of science ‘realism’ signals a number of analyses
and approaches:
Who has said what about this?
Hume
See above. That’s enough Hume – Ed.
J.S.Mill
Constructed
logical rules for determining when, in science, we may justifiably conclude
that two events are causally connected:
Method
of Agreement
If two or more instances of the
phenomenon under investigation have only one circumstance in common, the
circumstance in which alone all the instances agree is the cause (or effect) of
the given phenomenon.
Method
of Difference
If an instance in which the phenomenon under investigation occurs, and an
instance in which it does not occur, have every circumstance in common save
one, that one occurring in the former, the circumstance in which alone the two
instances differ is the effect, or the cause, or an indispensable part of the
cause, of the phenomenon.
Method
of Concomitant Variation
The magnitude of a phenomenon P is a function of
factors A, B, C....
The set of factors on the right hand side of
this equation is the full cause of P, while each of the relevant factors
is a partial cause.
(System of
Logic; Book III, Chs 1-8)
John Mackie (1917-1981)
1. Introduces the idea of a field:
·
This
meets the problem that the causes of a simple event like the matchhead igniting
seem on the face of it to be infinite in number.
·
In
Mackie’s analysis the background conditions and the counterfactual conditions,
are set aside as part of the field.
This also solves familiar problems such as:
‘Since it is normal for people to be striking
matches and lighting cigarettes in a residential flat, but a gas leak is
abnormal and should not occur, we may well say that the explosion which wrecked
this block of flats was caused by the presence of a quantity of gas rather than
that it was caused by Jones lighting his cigarette’.
2. INUS Cause
·
Frequently
it is not only the case that (Mackie pp 61-2)
‘All ABC are followed by P’
but also
‘All DGH are followed by
P’;
·
It
could be that
‘All ABC and/or All DGH and/or
All JKL are followed by P’;
‘All P are preceded by ABC or
DGH or JKL or ABCDGH or ABCJKL
or DGHJKL or ABCDGHJKL’
·
‘X
is a necessary condition for Y’means when an event of type Y occurs an event of
type X also occurs;
‘X
is a sufficient condition for Y’ means when an event of type X occurs an
event of type Y also occurs;
·
Then
[ABC or DGH or JKL] - is a condition which is both
necessary and sufficient for P;
·
and
[ABC] is a condition which
is sufficient but not necessary for P
[DGH] is a condition which
is sufficient but not necessary for P
[JKL] is a condition which
is sufficient but not necessary for P;
[ABCDGH] is a condition
which is sufficient but not necessary for P
[ABCJKL] is a condition
which is sufficient but not necessary for P
[DGHJKL] is a condition
which is sufficient but not necessary for P
[ABCDGHJKL] is a condition
which is sufficient but not necessary for P
·
Each
single factor (A, B, C, D, G, H, J, K, L) is neither necessary nor
sufficient for P;
·
But
each is clearly related to P in a significant way:
A (...N) is an Insufficient but Non-redundant part
of an Unnecessary but Sufficient condition for P
example
Wesley Salmon (b.1925)
Two
kinds of causal mechanism:
1)
spatiotemporally continuous causal processes that transmit causal influence
from one part of spacetime to another.
(Note the term ‘process’).
2)
causal interaction: when two or more causal processes intersect in spacetime
they may or may not produce lasting modifications in one another
These
in turn enable us to sort out two aspects of causal explanation:
1) aetiological
explanation: tells the story of how one event caused another and so on – a
caribou died 30,000 years ago, its carcass was preserved in ice for many millenia,
later (5,000 years ago) a bone was found by a human artisan, s/he
carved it into a useful and decorative object.
2) constitutive
explanation: the pressure exerted by a gas on the walls of a container is
explained in terms of momentum changes between the molecules and the walls
(this is like temperature and ice, bricks and glass, branches and cradles,
sugar and syrup).
3)
Salmon also wants to solve a problem from probability that we have met
before.
·
Hempel
argues that we have an explanation when we have a set of conditions and
probabilistic ‘laws’ such that the combination of conditions and laws means
that there is a high probability that the explanandum would occur.
·
However,
supposing it were the case that overall it turns out that 20% of HIV positive
people contract AIDS. Are we less
likely to say that HIV causes AIDS than in the alternative case that 80% of HIV
positive people contract AIDS? In
either case HIV looks like an INUS cause of AIDS.
·
And Salmon would want to say that we know HOW
HIV causes AIDS (attacking the immune system, causing elements of the immune
system to misrecognise cells, .... ) so there is more to the relationship
between HIV and AIDS than constant conjunction or regularity, as well as more
to it than prediction.
‘On the view of
causality I am advocating, causal
connections exist in the physical world and can be discovered by empirical
investigation’. (p23).
Salmon’s
philsophy of causality
‘involves relinquishing rational expectability as a
hallmark of successful scientific explanation.
Instead of asking whether we have found reasons to have expected the
event to be explained if the explanatory information had been available in
advance, we focus on the question of physical mechanisms. Scientific understanding, according to this
conception, involves laying bare the mechanisms – aetiological or constitutive,
causal or noncausal – that bring about the fact to be explained. If there is a stochastic process that
produces one outcome with a high probability and another with low probability,
then we have an explanation of either outcome when we cite the stochastic
process and the fact that it gives rise to the outcome at hand in a certain
percentage of cases. The same circumstance
– the fact that this particular stochastic process was operating – explains the
one outcome on one occasion and an alternative on another occasion.’. (p328)
Bas van Fraassen (b.1941)
Against
philosophers like Mackie and Salmon van F argues, following Hanson:
There are as many causes of x as there are
explanations of x. Consider how the cause of death might hav ebeen set out by a
physician as ‘multiple haemorrhage’, by the barrister as ‘negligence on the
part of the driver’, by a carriage builder as a ‘defect in the brakeblock
construction’, by a civic planner as ‘the presence of tall shrubbery at the
turning’. N R Hanson Patterns of
Discovery 1958 p54
example The judge asks Robber Robert why he robbed the bank. RR answers: ‘because that’s where the money
was.’
Judge: why rob the bank (as opposed to live a law abiding life)?
RR: why rob the bank (as opposed to the chemists)?
:
‘It
is not the case that the meaning of the sentence ‘A is the cause of B’ depends
on the nature of the phenomena A and B, but that this meaning depends on the
context in which this sentence is uttered.
The nature of A and B will in most cases play a role, indirectly, but it
is in the first place the orientation or the chosen point of view of the
speaker that determines what the word cause is used to signify.’