Updated:    03 March 2000


The Realist Picture



       Start with observations


       Seek explanations


       Produce theories


       Explain by reference to the unobserved



       Inference to the best explanation

                   Galileo - mountains on the moon

                   Einstein - atoms via Brownian motion

                   Thomson - electrons via scintillations



       Confirm by successful novel predictions




The theory provides a literally true (or truth-like) account of the underlying mechanisms in the world



Real realism –


truth as correspondence


reject reconstruals of truth (eg Peirce)



Explanatory Realism




Aim of science is the truth-related aim of having theories of ever greater verisimilitude.



Problems:               meaning of approximate truth

                                                       evidence for it





Observational success of science



Science uses IBE



Use IBE in your theory of science



What is it about today’s theories that enables them to give better predictions?



theories are more approximately true



advanced in contexts of Kuhnian scepticism







Historical sources



Limited epistemic skepticism


How do you know about electrons ?



Experience is the source of all knowledge, don’t have experience of electrons.



Limited - knowledge of observable states




Limited semantic skepticism



What do you mean?




Cannot give verbal definitions or ostensive examples for theoretical terms.



No more meaning than Hodge’s uninterpreted symbols






       theories are just predictive tools



1. Semantic


       T-terms lack meaning


       T-sentences lack truth-values



2. Epistemological


T-terms have meaning and T sentences have truth-values.  But utterly unknowable.




Constructive Empiricism



van Fraassen: The Scientific Image



aim of science: empirical adequacy



scientist does not believe a theory



scientist “accepts” a theory



       = believing in its predictive success




Objections to Explanatory Realism



Nothing to explain.



Theories picked for predictive power. That is why they are predictively successful.





- question begging - instrumentalist challenges its use as an epistemic tool in science


- explanation not linked to truth




no satisfactory account of verisimilitude (Laudan : Science and Values)




historical record is dubious (Laudan)




Underdetermination of theory by data.


Constructive Empiricism


1.    semantic realism


2.         Not traditional scepticism


       IBE ok from observables to observables


Crucial to distinquish between:

       O and T

       O and non-O


       i) Schlick : O

                   absolute certainty

                   inner experience - sense data


       ii) Carnap - matter of degree

                   quickly, accurately, confidently decide


       iii) van Fraassen - biological basis - what humans could (if suitably located) settle by using unaided senses





Local realism        



aim of science goes beyond that of empirical adequacy



Inference to the Best Explanation


global use



Argues for TV on the grounds that it provides best explanation of increasing observational successes of science


local uses


Seeks to justify positing atoms, electrons etc


Miller “book length argument for realism”




Underdetermination of theory by data






see hand-out


Underdetermination by the actual available data



Threat to IBE ?



Agnostic realism

       - wait and see




Undetermination of theory by all actual and possible data



For any theory T1 there is a theory T2 :



T1 and T2 are incompatible.



T1 and T2 are empirically equivalent


T1 and T2 are fare equally well on all other epistemic principles of theory choice.




Strong UTD - applies to all theories



Weak - applies to some theories



Observationally omniscient God



What hope for realism?



Inter-Galactic Conference


Newton ...  Einstein


Notwen...   Nietsnie