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Scientific Realism Structural Realism And Constructive Empiricism Notes

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Scientific Realism & alternatives Understanding Philosophy of Science - J. Ladyman
? Scientific realism is roughly the view the we should believe in the unobservable objects postulated by our best scientific theories.
? "Once we adopt the primary/secondary distinction we need to explain the relationship between our experience of things and their primary properties, and also how we can know about the primary properties of things at all."
? Metaphysical realism: our language refers to (and sometimes says true things about) a mind independent world.
? Direct realism: there are external objects that exist independently of our minds and which we directly perceive with the senses.
? Ideaism [sic]: We do not directly perceive objects but rather our minds' own ideas/representations of the world. o NB not a thesis about what exists, so compatible with e.g. metaphysical realism.
? Causal realism: there are external objects that exist independently of our minds and which cause our indirect perception of them via the senses.
? Berkeley denied the existence of matter and the distinction between primary and secondary properties.
? Logical positivism: the content of our thoughts must somehow be tied to ideas the mind acquires through sensory experience. This implies that no matter of fact that can be intelligibly or meaningfully thought about can go beyond all possible experience.
? Many empiricists take our knowledge of our sensory states to be foundational.
? Semantic instrumentalism: the theoretical terms of scientific theories should not be taken literally as referring to unobservable entities, because they are merely logical constructs used as tools for systematising relations between phenomena.
? Reductive empiricism: theoretical terms can be defined in terms of observational concepts; theories shouldn't be taken as literally referring to unobservables.
? "Some forms of antirealism are based not on the elimination of theoretical terms, but on theories of truth that deny the realist concept of truth as correspondence between language and the world."
? (Traditional) Realism involves 3 commitments:

1. Metaphysical commitment to the existence of a mindindependent world, including unobservables.

2. Semantic commitment to literal interpretation of theories and a correspondence theory of truth.

3. Epistemological commitment to the claim that we can know that our best current theories are approximately true &
successfully refer.
? Van Fraassen accepts 1 and 2 but not 3. o "[A]cceptance of the best theories in modern science does not require belief in the entities postulated by them."
? Objections to constructive empiricism: o Line between observable and unobservable is vague and changes with time

It grants ontological significance to an arbitrary distinction. o Underdetermination of theory by evidence is the only positive argument for adopting constructive empiricism, and this isn't a very good argument. (See Psillos)
? vF agrees that unobservable entities may exist, but thinks the boundary between what we can and cannot know exists coincides with the (changing) boundary between the observable and unobservable. o The 'able' in observable refers to our limitations qua human beings. o But then critics ask why we're allowed to imagine changing our spatiotemporal location but not our sensory apparatus.
? "Realists have argued that constructive empiricism depends upon a substantive distinction between acceptance and belief that is simply not available." o Objection: belief has the extra causal role of disposing someone to assert, "I believe T to be true".
? But Horwich argues that such differences in behaviour are the result not of a difference between belief and acceptance but are the product of 'philosophical double-talk'.
? "Constructive empiricism is an idealisation, but to idealise here seems legitimate since the realist has just as many if not more problems with partial belief or belief in partial or approximate truth, as van Fraassen does with partial empirical adequacy." 'A Confutation of Convergent Realism' - Larry Laudan
? "Taking the success of present and past theories as givens, proponents of CER claim that if CER were true, it would follow, as a matter of course, that science would be successful and progressive. Equally, they allege that if CER were false, the success of science would be 'miraculous' and without explanation."
? "The realist sense of reference is a rather liberal one, according to which the terms in a theory may be genuinely referring even if many of the claims the theory makes about the entities to which it refers are false."
? "To have a genuinely referring theory is to have a theory that 'cuts the world at its joints', a theory that postulates entities of a kind that really exist." o "But a genuinely referring theory need not be such that all - or even most - of the specific claims it makes about the properties of those entities and their modes of interaction are true."
? Part of what separates the realist from the positivist is the former's belief that the evidence for a theory is evidence for everything the theory asserts.
? "If the realist once concedes that some unspecified set of the terms of a successful theory may well not refer, then his proposals for restricting 'the class of candidate theories' to those that retain reference for the prima-facie referring terms in earlier theories is without foundation."?

"[O]n the best-known account of what it means for a theory to be approximately true, it does not follow that an approximately true theory will be explanatorily successful." o E.g. truth content being greater than falsity content, whatever this means.
? Even if the realist had a semantically adequate characterization of approximate truth, and even if that semantics entailed that most of the consequences of an approximately true theory would be true, she would still be without any criterion that would epistemically warrant the ascription of approximate truth to a theory.
? Reasons for realists not to adopt mature-immature science distinction: o Could make CER vacuous since mature sciences are generally defined as ones in which correspondence or limiting-case relations obtain invariably between any successive theories in that science. o Clearly parts of science (inc. many immature sciences) have been successful for a long time.
? "[S]ome of the most important theoretical innovations have been due to a willingness of scientists to violate the cumulationist or retentionist constraint which realists enjoin 'mature' scientists to follow."
? "In spite of his commitment to the growth of knowledge, the realist would unwittingly freeze science in its present state by forcing all future theories to accommodate the ontology of contemporary (mature) science."
? "[A] theory's ability to explain why a rival is successful is neither a necessary nor a sufficient condition for saying that it is better than its rival." 'Structural Realism: The Best of Both Worlds' - J. Worrall
? "A requirement for a convincing scientific explanation is independent testability...yet in the case of realism's 'explanation' of the success of our current theories there can of course be no question of any independent tests. Scientific realism can surely not be inferred in any interesting sense from science's success."
? "The chief argument against realism - the argument from scientific revolutions - is based precisely on the claim that revolutionary changes have occurred in accepted scientific theories, changes in which the old theory could be said to 'approximate the new' only by stretching the admittedly vague and therefore elastic notion of 'approximation' beyond breaking-point."
? Development of science: essential cumulativity at the empirical level, with sharp changes (non-cumulativity) at the top theoretical level.
? Pessimistic meta-induction: the picture of theory change in the past seems to supply good inductive grounds for holding that those theories presently accepted in science will, within a reasonably brief period, themselves be replaced by theories which retain (and extend) the empirical success of present theories, but do so on the basis of underlying theoretical assumptions at odds with those presently accepted.

?

Then left with 2 options: Worrall's view, or conjectural realism: the genuinely theoretical, observation-transcendent parts of scientific theories are attempted descriptions of reality. o But this latter makes no concessions to the no miracles argument.
? "What is needed [for Putnam & Boyd to reply to Laudan] is a reasonably precise and independent criterion of maturity."
? "Fresnel completely misidentified the nature of light; but, none the less, it is no miracle that his theory enjoyed the empirical predictive success that it did; it is no miracle because Fresnel's theory, as science later saw it, attributed to light the right structure."
? "Thus, if we restrict ourselves to the level of mathematical equations - not, notice, the phenomenal level - there is in fact complete continuity between Fresnel's and Maxwell's theories."
? "On the structural realist view, what Newton really discovered are the relationships between phenomena expressed in the mathematical equations of his theory, the theoretical terms of which should be understood as genuine primitives." 'What is Structural Realism?' - J. Ladyman
? Structural realism allegedly (a) avoids the force of the pessimistic meta-induction by not committing us to belief in the theory's description of the furniture of the world, and (b) does not make the success of science seem miraculous, by committing us to the claim that the theory's structure, over and above its empirical content, describes the world.
? Worrall's paper is ambiguous as to whether structural realism is metaphysics or epistemology. o It needs to be the former if it's going to gain an advantage over traditional realism.
? "If one replaces the conjunction of assertions of a first-order theory with its Ramsey sentence, the observational consequences of the theory are carried over, but direct reference to unobservables is eliminated." o NB still states that they exist.
? Epistemological structural realism: the objective world is composed of unobservable objects between which certain properties and relations obtain; but we can only know the properties and relations of these properties and relations, that is the structure of the objective world.
? But structure is not sufficient to uniquely pick out any relations in the world.
? "[I]f we treat a theory just as its Ramsey sentence then the notion of theoretical equivalence collapses onto that of empirical equivalence." o So this interpretation doesn't do justice to Worrall's intention. o "The problem of ontological discontinuity is left untouched by simply adopting Ramsification."
? "Psillos (1995) claims that structural realism presupposes a distinction between the form and content of a theory, or between our ability to know the structure and our ability to know the nature of the world."

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