Convention is essentially that the text of a treaty is decisive unless it either leaves the meaning ambiguous, or obscure, or leads to a result that is manifestly absurd or unreasonable. Recourse to "supplementary means of interpretation" is allowed only in that case, like the preparatory works, also known by the French designation of travaux préparatoires. Philosophies Over time, various methods of statutory construction have fallen in and out of favor. Some of the better-known rules of construction methods are: The golden rule The literal rule The mischief rule The purposive approach Statutory interpretation methods Within the United States, purposivism and textualism are the two most prevalent methods of statutory interpretation. "Purposivists often focus on the legislative process, taking into account the problem that Congress was trying to solve by enacting the disputed law and asking how the statute accomplished that goal." Purposivists believe in reviewing the processes surrounding the power of the legislative body as stated in the constitution as well as the rationale that a "reasonable person conversant with the circumstances underlying enactment would suppress the mischief and advance the remedy" Purposivists would understand statutes by examining "how Congress makes its purposes known, through text and reliable accompanying materials constituting legislative history." "In contrast to purposivists, textualists focus on the words of a statute, emphasizing text over any unstated purpose." Textualists believe that everything which the courts need in deciding on cases are enumerated in the text of legislative statutes. In other words, if any other purpose was intended by the legislature then it would have been written within the statutes and since it is not written, it implies that no other purpose or meaning was intended. By looking at the statutory structure and hearing the words as they would sound in the mind of a skilled, objectively reasonable user of words, textualists believe that they would respect the constitutional separation of power and best respect legislative supremacy. Critiques of modern textualism on the United States Supreme Court abound. See also Interpretation Act Judicial activism Judicial interpretation Legal interpretation in South Africa Original intent — Original meaning — Textualism Pepper v. Hart [1993] AC 573 Rule of law Statutory term analysis UK Interpretation Act (1850) References Further reading CRS Report for Congress: "Statutory interpretation: General Principles and Recent Trends" (public domain - can be copied into article with citations) The multi-volume Sutherland Statutory Construction is the authoritative text