Fetching details from the dictionary...
theory
standard procedure; common strategy; established tactics
料理にもセオリーがある。
Even cooking has its theory.
彼はセオリー通りに動いて相手を崩した。
He played by the book and broke down his opponent's defense.
古いセオリーはデジタル時代に通じなくなった。
Old theories no longer hold in the digital age.