The degree builds upon the work of the Bachelor of Sacred Theology and the Licentiate of Sacred Theology. Normally, the STB is earned in three years, provided the candidate has at least two years of undergraduate study of philosophy before entering an STB program. The STL is normally earned in an additional two years, and the STD is earned after the writing, defense and publication of the doctoral dissertation. At institutions that offer both civil and church doctorates, the requirements of the STD will usually—although not always—be shaped so that those reading for the award can receive a ThD or PhD in the process of meeting the requirements of the STD. This compares with, for example in North American institutions, the four-year program for a BA at many universities, a two-year program for an MA, and the writing and successful defense of the doctoral dissertation for the PhD or ThD. A sketch of the degree cycle and requirements for ecclesiastical degrees can be found in John Paul II's apostolic constitution, Sapientia Christiana. The STD, or the Doctor of Canon Law, is the preferred qualification for teaching theology or canon law on a Catholic university faculty or for holding certain other posts of administration. In addition, the STD is usually required for a permanent post on the theology faculty of an ecclesiastical or pontifical university. However, this requirement can be waived if a teacher holds an STL. John Paul II's Sapientia Christiania notes that in the event where a doctorate is non-canonical, "the teacher will usually be required to have at least a canonical licentiate.". In the US, although it may have more stringent entry requirements than a PhD in theology, it is a research degree that is considered by the US National Science Foundation to be the equivalent of a Doctor of Philosophy.
This degree has sometimes been referred to as Sacrae Theologiae Professor, "Professor of Sacred Theology", even when the individuals holding it were not professors in the present-day sense of the word; this stems from the mediaeval usage of 'professor', 'doctor' and 'master' as synonymous terms for the highest degree. Inscriptions survive on several ancient monuments in English and Welsh and Church of Ireland churches and in University buildings which use this abbreviation to denote holders of the degree of Doctor of Divinity. The practice of denoting this degree as STP or STD has now been discontinued.
