Decision theory is the study of principles and algorithms for making correct decisions—that is, decisions that allow an agent to achieve better outcomes with respect to its goals [1].
See also: Game Theory, Robust Agents, Utility Functions
The best known decision theories are Causal Decision Theory (CDT) and Evidential Decision Theory (EDT). On LessWrong, an alternative family of decision theories has been discussed heavily with the varying names of Updateless Decision Theory (UDT), Timeless Decision Theory (TDT), and Functional Decision Theory (FDT).