Ad hoc hypothesis

An ad hoc hypothesis (Latin - Ancient Greek word mixed ) is an auxiliary hypothesis, which is an ad hoc basis, that is established for a particular case in order to meet critical observations or arguments that could disprove the challenged theory.

Even in natural science theories are young, often supported by such assumptions. Famous examples are the Lorentz contraction hypothesis fitzgerald - with which the negative result of Michelson -Morley experiment should be explained; and Einstein's cosmological constant, which should prevent a company resulting from his theory expansion or contraction of the universe. Paul Feyerabend dedicated in his standard work on critical theory of science, Against Method, Section 8 of detail of the ad hoc hypothesis. He said it: " give the ad hoc hypotheses new theories a breathing space, and they indicate the direction of future research. "

Scientific examples

• Max Planck founded with the ad hoc assumption that the physical effect can occur only in multiples of a quantum of action quantum physics.

• In his formulation of the model of the atom Niels Bohr presented on the postulate that the electrons emit in the radial acceleration on their orbits no radiation.

• The continuous spectrum of beta decay was explained by Wolfgang Pauli by the ad hoc hypothesis of the existence of a hitherto unobserved and massless elementary particle, the neutrino.

Popper's critique of the formation of ad hoc hypotheses

Karl Popper sees in the formation of ad hoc hypotheses, the risk of a form of immunization strategies against criticism, which he denounces as a conventionalist twist or conventionalist strategy. According to Popper's opinion the establishment of ad hoc hypotheses are often done with the intent to try to rescue a pet theory: