1. Giving the Devil His Due: Relevance in Mechanistic Explanation
Carl F. Craver

2. “Relevance” is multiply ambiguous
Personal relevance: What are the psychological mechanisms by which things that are relevant to me are distinguished from things that are irrelevant to me? (Thagard’s talk)
Evidential relevance: When is a piece of evidence relevant to evaluating a hypothesis? (Kuorikoski?)
Explanatory relevance: When is something explanatorily relevant to some phenomenon we want to explain? And when is it irrelevant?

3. Desiderata for a theory of explanation:
Descriptive:
The analysis should fit uncontroversial exemplars of excellent scientific explanations and should not fit uncontroversial exemplars of failed scientific explanations.
Demarcation:
The analysis should distinguish scientific explanation from other kinds of scientific achievement (e.g., description, prediction, modeling, and taxonomy).
Normativity:
The account should provide relatively clear rules or norms by which scientific explanations ought to be assessed.

4. Two Kinds of Explanatory Relevance: Etiological and Constitutive

5. Outline 1. The Covering Law Model
2. Classic Problems and the Causal Solution
3. Problems of Constitutive Explanation
4. Applications to Contemporary Issues
2000-Present
Now

6. 1. The Covering Law (CL) Model (1943-1980)
Explanations are arguments. The premises (the explanans) are statements of law and descriptions of conditions; the conclusion (the explanandum, is the thing to be explained.
Explanation is rational expectation: An explanation shows the explanandum phenomenon was necessary or probable given the laws of nature and the relevant empirical conditions.
Explanations work ”covering” the explanandum by the laws of nature.

7. A classic example of CL explanation
Laws (i.e., true generalizations)
Conditions
Explanandum
Law: Light travels in straight lines
Θ = 70°
h = 10
x = 8.19 m

8. 2. Three Problems of Relevance (1960-1989)
Explanatory Relevance
Asymmetry
Non-Explanatory Correlations

9. No male who takes birth control pills faithfully every day gets pregnant.
Petri is a male and takes his birth control pills faithfully every day.
Petri is not pregnant.

10. Law: Light travels in straight lines
Θ = 70°
x = 8.19 m
h = 10

11. The Fitzroy glass crystalized yesterday at 3PM.
Whenever the Fitzroy crystalizes, a storm arises.
A storm arose yesterday.

12. This correlational data
A and B are mutually probabilistically dependent,
A and C are mutually probabilistically dependent,
B and C are mutually probabilistically dependent,
B and C are probabilistically independent conditional on A
is consistent with the following causal structures:
A -> B and C
B -> A -> C
C -> A -> B A B C B C A B C A B C A

13. It’s about causation! Not expectation , Production.
Not necessarily an argument, but a description of all and only the relevant causes.
To explain a phenomenon is to show how it is situated in the causal structure of the world.
Salmon (1984)

14. Causation
X is a causally relevant to Y (and so explanatorily relevant to Y) iff one can change the value of Y with an ideal intervention on X (Woodward 2003)
Slogan: Causal relevance is what we detect in a well-controlled experiment.
Note: Metaphysically neutral

15. We cannot get Petri pregnant by forcing him to stop taking birth control pills.

16. We cannot change the height of the flagpole by changing the elevation of the sun or the length of the shadow.

17. We cannot change the weather by forcing crystals to form in the Fitzroy glass.

18. Evidential Relevance vs. Explanatory Relevance
Evidential relevance (roughly): Does learning fact F change the probability I would assign to proposition P?
Barometers and storms
Person P takes birth control pills.
The shaddow’s length gives us reason to believe the flagpole’s height is what it is.
Explanatory relevance is about making a difference.

19. 3. When Details Don’t Matter: Abstract and Higher-Level Causes
Why did the water freeze rather than remain liquid?
H1: The room was -18.6° C.
H2: The room was < 0° C.
Why did the water freeze in exactly 72 minutes rather than at some other rate?

20. Another example Why did the neuron release neurotransmitters?
H1: Because of the particular configuration of sodium and potassium ions in and around the neuron’s membrane.
H2: Because the axon terminal depolarized beyond the threshold required for opening calcium channels.

21. A General Approach to Abstract Causes
Step 1: Characterize the phenomenon precisely using a contrastive formulation
(e.g., fluid vs. solid)
Step 2: Find the value of X that marks the boundary between Y = y and Y = y’
(e.g., below 0 C/above 0 C)
These are “switch-points”
*Changes in the value of X that cross switchpoints make a difference to Y and so are relevant to Y.
*Changes in the value of X that do not cross switchpoints make no difference to Y and so are not relevant to Y.

22. This Experimental Trick Shows When the Details Don’t Matter

23. 3. Constitutive (Mechanistic) Explanations

24. The Problem of Constitutive Relevance
Which entities, activities, and organizational features are components in the mechanism and which are not?
What is the difference between a neural correlate and a component in the mechanism?
What is required to integrate levels of mechanisms?

25. Problem-Cases for a Theory of Constitutive Relevance
Sterile Effects (Byproducts). Effects of components in the mechanism that make no difference to the behavior of the mechanism (e.g. Changes in cerebral blood flow).
Irrelevant Parts and Properties. Parts or properties associated with the mechanism but irrelevant to its functioning (e.g. Blessed NMDA receptors or irrelevant intracellular molecules).
Indirect Effects. Parts or properties that, when manipulated, change how the mechanisms works but that are not part of the mechanism. (e.g., lesion studies, stimulation studies)

26. Experiments for Establishing Constitutive Relevance

27. Activation Experiments
Common LTP Protocol
Produce LTP; measure changes in intracellular concentrations
fMRI
One Worry:
“Merely Correlative”
A sense in which this is false.
A sense in which this is true: Sterile Effects. SE

28. Activation Experiments at one Level
Detect
Stimulate
Sterile Effect
Detect

29. Interference Experiments
NMDAR Antagonists
Gene Knockouts
One Worry:
Indirect effects
How Activation Helps

30. Interference Experiments at one level
Detect
Stimulate
Activation Experiments solve the problem of indirect effects.
Inhibit

31. Stimulation Experiments
Change Calcium concentrations
Stimulate post-synaptic cell.
One Worry:
Indirect Effects
How Interference Helps

32. Stimulation Experiments at One Level
Detect
Activation Experiments solve the problem of indirect effects.
Stimulate

33. Constitutive Relevance: Mutual Manipulability (Craver 2007)
x’s -ing is constitutively relevant to S’s -ing if
(i) x is part of S;
(ii) it is possible to manipulate S’s -ing by ideally intervening to change X’s -ing;
AND
(iii) it is possible to manipulate X’s -ing by ideally intervening to change S’s -ing

34. Problems Revisited
Sterile Effects. Changes in cerebral blood flow do not explain cognitive performance, though changes in blood flow are tightly correlated with cognitive performance.
Irrelevant Parts and Features. Blessed NMDA receptors induce LTP, but the blessing is irrelevant to how the mechanism works.
Indirect Effects. One can eliminate memory by lesioning the heart, but one cannot produce memories by intervening on the heart.

35. Some limits to this account
It is merely a sufficient condition, not necessary.
Redundancies may prevent effects of inhibition.
Parts that do not change during the activity of a mechanism will not activate during activation experiments.
(e.g., the axel on which a wheel rotates).
And it might not be sufficient
Background conditions
Increasing heart rate might prevent verb stem completion
Torturous verb stem completion might increase heart rate.
But perhaps this isn’t a problem:
The heart rates don’t match in these two condition

36. Some other indicators of relevance
1. Changing mechanistic components often has a specific (i.e., non- general) effect on the phenomenon in question. Changing background conditions often has very general (i.e., non-specific) effects.
But not always
A general rule of this sort excludes the possibility that one component figures in many mechanisms (false!)
2. Changing mechanistic components often has subtle effects on the mechanism; changing background conditions acts as a crude switch.
But not always.
A general rule of this sort excludes the possibility of components with crude effects and background conditions with subtle effects (false!)

37. INUS Condition (Mackie 1965; Couch 2010)
Perhaps Mutual Manipulability is only a test of relevance.
Perhaps that’s why it’s only a necessary condition
A more general account:
Insufficient but Non-Redundant part of an Unnecessary but Sufficient (INUS) Condition
((ABC)  (ABD)  (ADE)  (BCD)  …)  P

38. Advantages of the INUS Approach
1. Determinism/Local Supervenience.
Each disjunct is sufficient for the phenomenon.
Ideal of completeness in mechanistic explanation.
2. Multiple Realizability.
The antecedent is a disjunction.
3. Rules out Irrelevant Components
Hexed NMDA receptors.
((ABC)  (ABD)  (ADE)  (BCD)  …)  P

39. A Problem for the INUS account:
Suppose a variable in the mechanism either
a) is always, as an empirical matter of fact, deterministically linked to a “byproduct”
E.g., Changes in cerebral blood flow do not explain cognitive performance, though changes in blood flow are tightly correlated with cognitive performance.
Or b) is necessarily accompanied by other changes
E.g., being metal and conducting electricity
There is no empirical basis to exclude the byproduct as a non- redundant part of the sufficiency set.
Solution: Require that each INUS condition be a cause of (i.e., a difference maker for) the mechanism’s output.

40. Conclusion
A theory of explanatory relevance is necessary for an adequate philosophical theory of scientific explanation.
Etiological explanatory relevance can be defined in terms of manipulability.
This view acknowledges abstract and higher-level causes.
Constitutive relevance can be discovered through relations of mutual manipulability.
But constitutive relevance is best defined in terms of INUS conditions plus an added causal restriction.