From Logical Positivism to Scientific Realism

1. From Logical Positivismto Scientific Realism Theories don’t have to be true to describe what we observe correctly. … [As] far as science is concerned, all that matters when it comes down to it is getting the predictions right for what we observe. Lots of different theories that disagree about what the unobservable world is like could still agree in what they predict about the results of experiments Ladyman (123, 160)

2. Announcement The final exam is scheduled for 6:30 pm Thursday April 19 in SBE 1220

3. Positivist epistemology • Positivists hold that our knowledge is built up from basic beliefs which are self-evidently true (i.e. immune from doubt) • All other beliefs are justified either deductively or inductively from basic beliefs • Basic beliefs are called ‘protocol statements’: “first person, singular, present tense, introspective reports” (152).

4. Dilemma for Logical positivism • We (claim to) know lots about the world • We only know protocol statements and analytic truths • How to move from ‘private’ sense-data to ‘public’ objects? • Solution: “Proposition asserting the existence of physical objects are equivalent to ones asserting that the observer will have certain sequence of sensations in certain circumstances” (153).

5. Logical positivism: phenomenalism • Physical objects are “permanent possibility of sensation”; they are “logical constructions out of actual and possible sense experience” (ibid). • What about theoretical terms, terms such as ‘positron’ that refer to unobservable entities?

6. Logical positivism & theoretical terms • Given their commitment to empiricism, logical positivists face a difficulty with theoretical terms, namely how can they be ‘meaningful’? • How do terms get meaning for concept empiricism? • Built up from simple ideas. • What about ‘charm’?

7. Theoretical terms • One way to address the problem of theoretical terms is to think in terms of kinds of statements • Assertoric statements are those can be true or false; they assert something about the world • Consider ‘Wong is 2m tall’ and ‘Damn it!’ • Two options: • Statements using theoretical terms are not assertoric • Statements using theoretical terms are assertoric

8. First option: semantic instrumentalism • Statements using theoretical terms are not assertoric: • Some concepts are useful fictions—e.g. the ‘average male professor at Wilfrid Laurier’ • This position is semantic instrumentalism (155) • Statements involving them are not assertoric but they are useful. • On this view, theoretical terms do not literally refer to entities; they are useful tools to systematize relations between phenomena

9. Second option: Reductive empiricism • If you hold that statements using theoretical terms are assertoric, then you can define, or reduce, theoretical terms in terms of words that refer to everyday sensory experience • Reductive empiricism: “theoretical terms can be defined in terms of observational concepts, hence statements involving them can be assertoric” (155) • Since theoretical terms are given ‘operational’ definitions, they do not refer to unobservable entities.

10. First problem: Operational definitions introduce too many properties E.g. ‘100 degrees Celsius’ How to systematize the properties? Second problem: How is certain knowledge possible? Use of public language suggests that observation reports are fallible Problems for Reductive Empiricism

11. Reductive empiricism to scientific realism • However, you can maintain that theoretical terms do refer to unobservable entities, that is, what science tells us is literally true • It is the mind-independent world that makes our assertoric statements true or false. This view is related to the ‘correspondence theory of truth’ (157)

12. Three requirements of scientific realism (158) Metaphysical requirement: Entities or kinds of entities talked about S exist Existence of entities is independent of our knowledge and minds Semantic requirement: Statements about S are irreducible and are genuinely assertoric Truth conditions for statements of S are objective and determine the truth or falsity of those statements depending on how things are in the world..

13. Requirements of scientific realism • Epistemic requirement: • Truths about S are knowable and we do in fact know some of them, hence the terms of S successfully refer to things in the world • If you were a scientific realist about sub-atomic particles, then you are committed to the following: • Positrons exist mind-independently • Statements about positrons are about subatomic particles • These statements are true/false depending on how the world is • Truths about positrons are knowable, and we do have some

14. Anti-realism • ‘Anti-realism’ is the position that rejects any one of the three requirements of scientific realism, or a combination of them • You can deny the requirement that the truth conditions are determined by how things are in the world by challenging the correspondence theory of truth • How would you cash out the relation of correspondence in the correspondence theory if you were an empiricist? • Or, if you were a social constructivist, you would hold that truth is by convention

15. Anti-realism • Alternatively, you can challenge the claim that we should take what scientific theories tell us literally • Here think about the following observation about data and theory: Data are typically compatible with more than one theory. Some of these theories are incompatible with one another. • Which theory should we take to be literally true? • This is the problem of Underdetermination: theory is underdetermined by data. • We will examine the argument from underdetermination next week