In mathematics, specifically category theory, a doctrine is roughly a system of theories ("categorical analogues of fragments of logical theories which have sufficient category-theoretic structure for their models to be described as functors"[1]: 284 ). For example, an algebraic theory, as invented by William Lawvere, is an example of a doctrine.[1]: 289
The concept of doctrines was invented by Lawvere as part of his work on algebraic theories.[2][3]: 12 The name is based on a suggestion by Jon Beck.[3][4]
Generalised algebraic models, by Claudia Centazzo.
William Lawvere, Ordinal sums and equational doctrines, Lecture Notes in Math., Vol. 80 (Springer, Berlin, 1969).
Lawvere, F William (1975). "Introduction to Part I". Model Theory and Topoi. Lecture Notes in Mathematics. Vol. 445. pp. 3–14. doi:10.1007/BFb0061291. ISBN978-3-540-07164-8.;