Blackwell Reference Online

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Unification of theories is achieved when several theories T 1 , T 2 , …, T n previously regarded as distinct are subsumed into a theory of broader scope T *. Classic examples are the unification of theories of electricity, magnetism, and light into Maxwell's theory of electrodynamics, and the unification of evolutionary and genetic theory in the modern synthesis ( Mayr and Provine 1980 ). In some instances of unification, T * logically entails T 1 , T 2 , …, T n under particular assumptions. This is the sense in which the equation of state for ideal gases, pV = nRT , is a unification of Boyle's law, pV = constant for constant temperature, and Charles's law, V/T = constant for constant pressure. Frequently, however, the logical relations between theories involved in unification are less straightforward. In some cases, the claims of T * strictly contradict the claims of T 1 , T 2 , …, T n . For instance, Newton's inverse-square law of gravitation is inconsistent with Kepler's laws of planetary motion and Galileo's law of free fall, which it is often said to have unified. Calling such an achievement “unification” may be justified by saying that T * accounts on its own for the domains of phenomena that had previously been treated by T 1 , T 2 , …, T n . In other cases described as unifications, T * uses fundamental concepts different from those of T 1 , T 2 ... log in or subscribe to read full text