PH201/400 – Week 13 Scientific Explanation III

1. PH201/400 – Week 13 Scientific Explanation III

2. 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.

3. 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.

4. 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.

5. 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’.

6. Leading idea: • Our comprehension of the universe is increased as the number independent assumptions we require decreases. • Such a unification is explanatory.

7. 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.

8. 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.

9. 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K1N&GK2 N&GK3N&GF1

10. Condsider an alternative theory U: U= K1&K2&K3&F1 Obviously: UK1UK2 UK3UF1 Intuitively, N&Gachieves real unification while U is a spurious unification. The challenge is to account for this intuition.

11. 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?

12. According to Kitcher, an generalargument pattern consists of: • A schematic argument • Aset of filling instructions • A classification. • Analogy: Formal logic, which provides argument patterns (like modus ponens) and studies their general properties. • But the structures in science are different.

13. (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.

14. (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 counts as valid argument.

15. 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

16. 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

17. Classification • (i)-(ii) have the status of premises • (iv) is obtained from (i)-(iii) by substitution of identicals • (v) follows from (iv) using calculus

18. 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.

19. (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.

20. (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.

21. 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.

22. 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

23. Problems and Questions • 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.

24. 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)

25. Questions: • How could Kitcher respond to these criticisms? • If he can’t how damaging are they?

26. Rebooting Intuitions Morrison (2000) argues that the entire account get started on the wrong foot: Hence, the association of unification with explanation is a mistake. ‘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.’

27. 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.

28. (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.’

29. (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.

30. 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.  

31. 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?