There is no need to pursue this history further. With ash-Shafi‘i the great development of Muslim jurisprudence closes. Legislation, equity, legal fiction have done their parts; the hope for the future lay, and lies, in the principle of the agreement. The common-sense of the Muslim community, working through that expression of catholicity, has set aside in the past even the undoubted letter of the Qur’an, and in the future will still further break the grasp of that dead hand. It is the principle of unity in Islam. But there is a principle of variety as well. The four schools of law whose origin has been traced are all equally valid and their decisions equally sacred in Muslim eyes. The believer may belong to any one of these which he chooses; he must belong to one; and when he has chosen his school, he accepts it and its rules to the uttermost. Yet he does not cast out as heretics the followers of the other schools. In every chapter their codes differ more or less; but each school bears with the others; sometimes, it may be, with a superior tone, but still bears. This liberty of variety in unity is again undoubtedly due to the agreement. It has expressed itself, as it often does, in apocryphal traditions from the Prophet, the last rag of respect left to the traditionist school. Thus we are told that the Prophet said, “The disagreement of My People is a Mercy from God.” This supplements and completes the other equally apocryphal but equally important tradition: “My People will never agree upon an error.”