Sir John W. Salmond, Jurisprudence (1913)
“ Legislation is the declaration or enunciation of a principle by some adequate authority in the body politic; custom is the realisation or embodiment of a principle in a uniformity of practice; precedent is the judicial application of a principle to its appropriate facts; professional or expert opinion is the approval or recognition of a principle by the general voice of those whose business it is to know the law; agreement is the adoption of a principle by the consent of those whose interests are affected by it. ”
