The Soka Gakkai Dictionary of Buddhism
three proofs[三証] (Jpn san-sho )
Documentary proof, theoretical proof, and actual proof. Three standards set forth by Nichiren (1222-1282) for judging the validity of a given teaching. Documentary proof means that the doctrine of a particular Buddhist school is based upon or in accord with the sutras. Theoretical proof means that a doctrine is compatible with reason and logic. Actual proof means that the content of a doctrine is borne out by actual result when put into practice. Nichiren writes: "In judging the relative merit of Buddhist doctrines, I, Nichiren, believe that the best standards are those of reason and documentary proof. And even more valuable than reason and documentary proof is the proof of actual fact" (599).