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Demarcation “We [scientists] believe that the world is knowable, that there are simple rules governing the behavior of matter and evolution of the universe … [and] that the collection of these truths is what we call physical science. Any intelligent alien anywhere would have come upon the same logical system as we have to explain the structure of protons and the nature of supernovae. “This statement I cannot prove. This statement I cannot justify. This is my faith.” Sheldon Glashow, Nobel Laureate Physics, Harvard

The commitments of Glashow’s credo:  Epistemological: the world is knowable and the physical sciences have a lot of this knowledge  Simplicity: there are simple rules governing the behavior of matter and evolution of the universe  Realism and, thus, intersubjectivity: any intelligent alien anywhere would have come upon the same logical system as we have to explain the structure of protons and the nature of supernovae.  Fallibilism: This statement I cannot prove. This statement I cannot justify. This is my faith.

Commitments displayed in The Elegant Universe  Epistemological:  If a theory (such as String Theory) isn’t testable, then no one should believe/accept it whatever its other merits.  If String Theory isn’t testable (e.g., strings by hypothesis can not and will not be observed), one needs to worry if it is science or, rather, philosophy – that is, metaphysics in Ayer’s sense.  Quasi (at least) Metaphysical:  There is “a theory of everything,, even if we don’t yet know what it is, and it is simple and elegant.

Commitments displayed in The Elegant Universe  Aesthetic/theoretical/epistemological and/or metaphysical:  Simplicity  Elegance  Unification  Unifying Quantum Theory and Relativity  The physics of the very small and the big (including the very big)  Indeterminacy (at the quantum level) and Determinacy at the macroscopic level

Demarcation  A.J. Ayer:  Logical Positivism (Logical Empiricism)  Distinguishing science from non-science (including metaphysics) and from pseudo-science  At its core: logic and empiricism  Arguing for the positive difference science can make in the world.  Seeking to expose what makes non- or pseudo- science just that.

Demarcation  The target: (A particular form of) Metaphysics  Any effort to discover a “transcendent reality” or any claim to have discovered aspects of such a realty  Transcendent reality: A reality that transcends (goes beyond, hides behind…) the world of science and common sense.  Verifiability: Scientific claims and theories, unlike non- scientific claims and theories (e.g., metaphysical claims) can be verified (shown to be true) through observation.  A sentence is factually significant (meaningful) … if, and only if, there are observations that would lead one to accept that sentence as true – or reject it as being false.

Demarcation  If, alternatively, the truth or falsity of a sentence is consistent with any and all future observations, it is a pseudo sentence or claim.  What of kinds of sentence (say, ethical, or a line of poetry or of a novel) that don’t meet this criterion but also don’t claim to be scientific. Are they “meaningless”?

Demarcation  What about sentences (say, ethical such as ‘Murder is wrong’, or a line of poetry or of a novel) that don’t meet this criterion but also don’t claim to be scientific. Are they “meaningless”?  Literally, yes. Though they may carry emotional meaning for an individual, they lack factual significance.  They do not constitute a claim about a matter of fact.

Demarcation  Fine-tuning the criterion and argument for it  The distinction between “practical verifiability” and “verifiability in principle”  Some sentences are practically verifiable; we can undertake the observations that demonstrate their truth.  Some sentences cannot be verified practically (or we do not feel the need to attempt to verify them) but are ‘verifiable’ in principle: Simply because we lack the physical capacity or technical means to do so (that red school house…). Yet we do know what observations of matters of fact would verify them.

Demarcation  Fine-tuning the criterion and argument for it  Understanding ‘to verify’ as to establish or discover the truth of a sentence, we need to decide between ‘strong’ or conclusive verifiability, and a ‘weaker’ sense.  Conclusive verifiability would call for too much, ruling out the laws and generalizations so important to science that yield an infinite number of observational predictions as anything more than “nonsense,” albeit “important nonsense”.

Demarcation  But as such statements are important features of science (if not basic to science), ruling them out as “nonsense” is wrongheaded.  Better to adopt a more reasonable but still clear criterion involving verifiability:  Namely, a sentence or claim of any sort is genuine only if it is verifiable, and it is verifiable if it possible for observations/experience to render it probable.

And now, as Monty Python would say, for something completely different (?)  (Sir) Karl Popper  Science the autumn of 1919, wrestling with the question “Is there a criterion for the scientific character or status of a theory?”  Distinct from the question “When is a theory true or acceptable?”  Alternatively put, what distinguishes a genuinely empirical method and a non- or pseudo empirical method?

Popper’s Falsifiability  Comparing 4 then popular and much discussed theories: Relativity, Marxism, Freudianism, and Adlerian Psychology  Although each of the latter three might contain important truths or insights, and although they are said to enjoy extensive confirmations (supporting observations and experiences), they turn out not to be scientific.  Although it was unclear at the time whether Einstein’s theory was true, it turns out to be scientific.

Popper’s Falsifiability  The criterion used to make these judgments and to be generalized: Falsifiability  Every genuinely scientific theory is a prohibition. It forbids certain things to happen.  A theory that is not falsifiable (refutable) by any conceivable event is not scientific.  Relativity does prohibit or forbid certain things to happen. Moreover its predictions are “bold” and “risky”. And 1919 brought about the first important confirmation of it.

Popper’s Falsifiability  The criterion used to make these judgments and to be generalized: Falsifiability  So what is wrong with the other three?  After all, Popper concedes they enjoy numerous confirmations (or verifications in Ayer’s terms).  But Popper also maintains that numerous confirmations should not count unless they are bold and risky.  For Popper, none of the three is falsifiable.  But what does this mean?

Popper’s Falsifiability  The criterion used to make these judgments and to be generalized: Falsifiability  For Popper, none of the three is falsifiable.  But what does this mean?  Two (exclusive?) senses:  Each theory is compatible with any and all relevant observations, events, experiences, etc.  Advocates of each theory see confirmations everywhere and explain away apparent counter- examples.

Similarities and Differences  Shared interest in demarcation criterion  Emphasis on matters of fact, observations, experience…  Emphasis on evidential relations as logical.  The difference:  Ayer emphasizing the importance of confirmation or verification  Popper drawing on the fact that while a generalization can never be proven (conclusively verified), it can be falsified.