 In a series of papers Carlos Alchourrón, Peter Gärdenfors and David Makinson created what they called a logic of theory change, later known as the AGM paradigm. Two particular kinds of change inspired their work: change due to deontic actions (Alchourrón) and change due to doxastic actions (Gärdenfors and before him Isaac Levi). Examples of deontic actions are derogation and amendment (laws can be annulled or amended), while contraction and expansion are analogous doxastic actions (beliefs can be given up, new beliefs can be added). Later the modal logic of such actions has been explored under the names dynamic deontic logic, dynamic doxastic logic and dynamic epistemic logic. (For the classic paper on AGM, see AGM 1985. For an introduction to dynamic deontic logic and dynamic doxastic logic, see Lindström and Segerberg 2006. We will return to this topic in Section 4, where it is viewed from the perspective of the field of artificial intelligence.