Definition: Regularity theory (RT) attempts to account for natural laws in a descriptive manner contra the necessitarian position (NT), which expresses the laws of nature as nomic necessity.
More about the term: According to the RT the fundamental regularities are brute facts; they neither have nor require an explanation. Regularity theorists attempt to formulate laws and theories in a language where the connectives are all truth functional. Thus, each law is expressed with a universal quantifier as in [(x) (Px ⊃ Qx)]. The NT states that there are metaphysical connections of necessity in the world that ground and explain the most fundamental regularities. Necessitarian theorists usually use the word must to express this connection. Thus, NT maintains must-statements are not adequately captured by is-statements (must ≠ is, or certain facts are unaccounted for).