Verifiability Falsifiability And Popper Notes

Verifiability and Falsifiability

Understanding Philosophy of Science – Ladyman

• Popper: there is a logical asymmetry between confirmation and falsification of a universal statement: no matter how many positive instances of a generalisation are observed it is still possible that the next instance will falsify it.

  • But one negative instance of a generalisation supposedly suffices to refute the theory.

  • There’s no positive support for the fittest theories, rather they are just those that repeatedly survive attempts to falsify them and so are the ones that are retained by the scientific community.

• “Popper must grant that there is no such thing as a completely conclusive refutation of a theory by experiment.” Which he does.

• You cannot argue from the fact that falsification is never completely conclusive to the conclusion that there is no logical asymmetry between confirmation and falsification.

• Examples of (probably scientific) statements which aren’t falsifiable (i.e. counterexamples to Popper):

  • Probabilistic statements – Popper thinks these aren’t scientific

  • Existential statements

  • Scientific principles like principle of the conservation of energy.

• Falsificationism is not itself falsifiable. Popper says this doesn’t matter

  • But surely it does if he wants to make philosophy scientific

• Notion of degree of falsifiability is problematic.

  • “The set of potential falsifiers for a universal generalization is always infinite, so there can be no absolute measure of falsifiability, but only a relative one.”

• “Our scientific knowledge does not seem to be purely negative and if it were it would be hard to see why we have such confidence in certain scientifically informed beliefs.”

  • The only reason an unfalsified hypothesis might seem worthy of retention is because it is more likely to be right! But this intuition ignores the fact that the set of potential falsifiers is infinite. But maybe we shouldn’t think in terms of sets of propositions (even though Popper clearly does). Possible worlds would present the same problem.

‘Positivism and Realism’ – Schlick

• The meaning of a question is clear “when and only when we are able to state exactly the conditions under which it is to be answered in the affirmative, or, as the case may be, the conditions under which it is to be answered in the negative.”

• “The meaning of a proposition consists…in this alone, that it expresses a definite state of affairs.”

• “[I]n order to find the meaning of a proposition, we must transform it by successive definitions until finally only such words occur in it as can no longer be defined, but whose meanings can only be directly pointed out.”

  • “The criterion of the truth or falsity of the proposition then lies in the fact that under definite conditions (given in the definition) certain data are present, or not present.”

• “We can understand in a proposition only what it communicates, and a meaning is communicable only if it is verifiable. Since propositions are nothing but vehicles for communication we can include in their meanings only what they can communicate. For this reason I should maintain that “meaning” can mean only “verifiable meaning”.”

• Laws of nature are not themselves (verifiable) statements but machines for generating statements which can then be tested.

‘Logical Positivism’ – Christopher Ray

• Isaiah Berlin counterexample to verificationist criterion of meaning:

  • This logical problem is a bright shade of green.

  • I dislike all shades of green.

  • Therefore I dislike this logical problem.

• Logically valid & grammatically correct, and an experiential statement has been deduced from the first statement, so Ayer’s criterion would say that the first statement is empirically meaningful.

• 2 attempts to resolve this:

1. Make ‘experiential statement’ mean ‘observation statement’. Then what is observable is what is ‘given’ in immediate sense experience and hence incorrigible.

   1. True experiential statements correspond in some straightforward way to the world. Logic is then used to analyse the connection via analytic rules of statements in ordinary language to the statements of a more elementary language pitched at the sensory level.

2. Elementary or ‘protocol’ sentences refer to public physical experience and cash out the content of that experience.

   1. Protocol sentences are supposed to provide a precise record of a scientist’s experience. Set within a given linguistic framework and the terms are given meaning by ‘meaning postulates’ – analytic rules connecting the terms to the synthetic observational claims made by the sentences.

   2. Carnap’s distinction between ‘formal’ and ‘material’ modes of speech: public basis for intersubjective agreement about experiences, and private content of subjective experience respectively.

   3. Judgments are framework-relative; there can be more than one physics.

The Logic of Scientific Discovery – Popper

• An inductive inference is one that passes from singular statements e.g. accounts of the results of experiments, to universal statements.

• We aren’t justified in reasoning in this way.

  • We would be if there were a principle of induction which would then make them deductive. But the principle of induction can’t be a logical truth and must be a synthetic universal statement. In which case the very same problems arise again for the justification of this statement.

• “So long as theory withstands detailed and severe tests and is not superseded by another theory in the course of scientific progress, we may say that it has ‘proved its mettle’ or that it is ‘corroborated’ by past experience.”

• Main reason for rejecting induction is that it doesn’t provide a suitable demarcation criterion between science and pseudo-science.

• “[P]ositivists, in their anxiety to annihilate metaphysics, annihilate natural science along with it. For scientific laws, too, cannot be logically reduced to elementary statements of experience.”

• The choice of demarcation criterion will have to be...

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