Academic tenure in the United States and Canada is a contractual right that grants a teacher or professor a permanent position of employment at an academic institution such as a university or school. Tenure is intended to protect teachers from dismissal without just cause, and to allow development of thoughts or ideas considered unpopular or controversial among the community. In North America, tenure is granted only to educators whose work is considered to be exceptionally productive and beneficial in their careers. Academic tenure became a standard for education institutions in North America with the introduction of the American Association of University Professors (AAUP)'s 1940 Statement of Principles on Academic Freedom and Tenure. In this statement, the AAUP provides a definition of academic tenure: "a means to certain ends, specifically: (1) freedom of teaching and research and of extramural activities, and (2) a sufficient degree of economic security to make the profession attractive to men and women of ability." Academic tenure (colleges and universities) Under the tenure systems adopted by many universities and colleges in the United States and Canada, some faculty positions have tenure and some do not. Typical systems (such as the widely adopted "1940 Statement of Principles on Academic Freedom and Tenure" of the American Association of University Professors) allow only a limited period to establish a record of published research, ability to attract grant funding, academic visibility, teaching excellence, and administrative or community service. They limit the number of years that any employee can remain employed as a non-tenured instructor or professor, compelling the institution to grant tenure to or terminate an individual, with significant advance notice, at the end of a specified time period. Some institutions require promotion to Associate Professor as a condition of tenure. An institution may also offer other academic positions that are not time-limited, with titles such as lecturer, adjunct professor, or research professor, but these positions do not carry the possibility of tenure and are said to be not "tenure track". Academic tenure's original purpose was to guarantee the right to academic freedom: it protects teachers and researchers when they dissent from prevailing opinion, openly disagree with authorities of any sort, or spend time on unfashionable topics. Thus academic tenure is similar to the lifetime tenure that protects some judges from external pressure. Without job security, the scholarly community as a whole may experience pressure to favor noncontroversial lines of academic