Ad hoc hypothesis

An ad hoc hypothesis is an auxiliary claim introduced chiefly to protect a theory from a specific counterexample, often without independent support.

Auxiliary hypothesis: A supporting assumption used alongside a theory to derive predictions or interpret evidence. Ad hoc hypotheses are auxiliary hypotheses added specifically to shield a theory from a challenge.
Progressive problemshift: A sequence of theory changes that predicts novel facts and gains empirical support. Unlike a merely defensive patch, progressive revisions produce testable successes beyond the original anomaly.
Neptune: The eighth planet from the Sun, discovered in 1846 after its position was predicted from orbital irregularities. The unseen planet explained Uranus’s anomalies and gained independent observational confirmation, unlike a bare protective patch.
Karl Popper: A twentieth-century philosopher of science who emphasized falsifiability as a criterion for scientific theories. Popper’s account made resistance to refutation central to evaluating protective hypotheses.
Falsifiability: The capacity of a claim to make predictions that could conflict with possible observations. A protective addition can weaken a theory’s falsifiability by ruling out apparent counterexamples.
Degenerating problemshift: A sequence of theory changes that accommodates known facts without producing novel predictive success. It captures how repeated protective amendments can signal stagnation in a research programme.
Vulcan (hypothetical planet): A hypothetical planet once proposed to explain anomalies in Mercury’s orbit but never observed. Vulcan illustrates a failed auxiliary explanation later displaced by general relativity.
Imre Lakatos: A philosopher of science who assessed research programmes by their progressive or degenerating development. His framework distinguishes productive theory revisions from adjustments that only accommodate known problems.
Duhem–Quine thesis: The thesis that hypotheses are tested together with auxiliary assumptions, not in isolation. It explains why a failed prediction does not identify which assumption needs revision.
Scientific theory: A coherent system of explanations that organizes evidence and supports testable predictions. Ad hoc hypotheses are judged by whether they strengthen or merely shelter the theory they accompany.

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PseudoscienceRelated: Repeated patches can shield pseudoscientific claims from failed predictions.