The nature and methodologies of science practice questions.

The no-miracles argument for scientific realism claims that

• scientific theories are accepted only when they have been proved true beyond any possibility of revision
• science has never yet abandoned a theory that made successful predictions
• any theory that saves the observable phenomena is thereby shown to describe unobservable entities correctly, whatever its history
• the predictive success of mature theories would be inexplicable unless their theoretical claims were approximately true

Answer: the predictive success of mature theories would be inexplicable unless their theoretical claims were approximately true

The argument is an inference to the best explanation applied to science as a whole. Its best-known opponent is the pessimistic meta-induction, which points to past theories that were predictively successful and are now regarded as false.

Van Fraassen's constructive empiricism holds that the aim of science is to produce theories that are empirically adequate, and that acceptance of a theory involves belief only that it is empirically adequate. This means that a constructive empiricist

• denies that theories about unobservable entities are even meaningful
• holds that a theory is true whenever it fits the observations made so far
• may use a theory about unobservable entities fully while withholding belief that its unobservable claims are true
• regards the distinction between observable and unobservable entities as having no bearing on science, since all evidence is theoretical

Answer: may use a theory about unobservable entities fully while withholding belief that its unobservable claims are true

The position is anti-realist about belief rather than about meaning or use: the theory is taken as literally construed and as a legitimate instrument of reasoning, and only the epistemic commitment is withheld. The standard objection targets the observable-unobservable line as arbitrary.

On the covering-law model, an explanation derives the event to be explained from laws together with statements of the initial conditions. The flagpole counterexample presses the objection that

• the length of a shadow can be derived from the height of the pole and the height from the shadow, yet only one direction explains
• no derivation of any observable event from laws has ever actually been carried out in practice
• the laws used in such derivations are only statistical, so no event can be strictly derived at all, which makes the model inapplicable outside physics
• the initial conditions in real cases are too numerous to be stated completely

Answer: the length of a shadow can be derived from the height of the pole and the height from the shadow, yet only one direction explains

Derivation is symmetric and explanation is not, so meeting the model's conditions is not sufficient for explaining. This is the standard motivation for causal accounts, on which the explanation follows the direction in which the process actually ran.

Inference to the best explanation concludes that the hypothesis which best explains the evidence is probably true. Van Fraassen's objection from the 'bad lot' is that

• no hypothesis has ever been shown to explain evidence better than all its rivals
• explanatory virtues such as simplicity are aesthetic and therefore play no part in science, so an inference that relies on them cannot be assessed at all
• the best of the hypotheses considered may still be the best of a poor selection, since we have no reason to think the true one was among them
• the evidence in scientific cases is never sufficient to distinguish between two hypotheses

Answer: the best of the hypotheses considered may still be the best of a poor selection, since we have no reason to think the true one was among them

The inference compares the candidates we happen to have thought of, and being the best available is not being probably true unless the truth is in the pool. Defenders reply that scientists do have grounds, from the history of the field, for thinking their pools are not that impoverished.

The logical positivists proposed the verification principle; Popper proposed falsifiability. Which statement states the difference between the two proposals?

• Both were offered as criteria of meaning, but Popper demanded conclusive verification by observation
• The verification principle was offered as a criterion of meaning, falsifiability as a criterion of demarcation
• The verification principle was offered as a criterion of demarcation, falsifiability as a rule for confirming laws
• Both were offered as criteria of demarcation, but the positivists admitted unfalsifiable theories into science

Answer: The verification principle was offered as a criterion of meaning, falsifiability as a criterion of demarcation

Ayer's principle declares a statement that no observation could verify to be without factual meaning, so metaphysics comes out as nonsense; Popper's criterion says only that an unfalsifiable theory is not scientific, and he explicitly allowed such statements to be meaningful and even fruitful.

Consider this derivation: no man who takes birth control pills becomes pregnant; Jones is a man who took birth control pills; therefore Jones did not become pregnant. Which defect in the covering-law model does the example expose?

• That the model cannot accommodate explanations appealing to statistical rather than universal laws
• That the model requires the event explained to have been predicted before it in fact occurred
• That a derivation can satisfy every condition the model sets while citing an irrelevant factor
• That the model cannot distinguish a genuine law of nature from an accidental generalisation

Answer: That a derivation can satisfy every condition the model sets while citing an irrelevant factor

The premises are true and the conclusion follows, so the formal conditions hold, yet nothing has been explained because taking the pills made no difference. This is the irrelevance objection, and it is distinct from the flagpole case, which attacks the model's failure to fix the direction of explanation.