The legal device is introduced to preserve the principle and the purpose for which the law was ordained. In Jewish law, likewise, the legal device was instituted not to circumvent the law, but to serve as a guard against the threatened neglect of a Biblical precept. It is scarcely necessary to stress that, as in the case of the Jewish people, changes, political, social and economic, have often taken place, the Jewish legislators felt impelled to contrive some legal instrument in order to preserve the idea and concept underlying a given precept. Such a device would help to maintain the Law and thus prove valuable in furthering the welfare of the individual, the group and the community.
M.S. Lew, “The Humanity of the Halachah,” Essays Presented to Chief Rabbi Israel Brodie on the Occasion of His Seventieth Birthday, ed. H.J. Zimmels, J. Rabbinowitz, I. Finestein (London: The Soncino Press Limited, 1967), 244.