Consequentialism is the ethical theory that people should choose their actions based on the outcomes they expect will result. How to judge outcomes is not specified, but there are many types of consequentialism that specify how outcomes should be judged. For example, utilitarianism holds that the best outcome is that which maximizes the total welfare of all people, and ethical egoism holds that the best outcome is that which maximizes their own personal interests. Consequentialism is one of three main strands of ethical thought, along with deontology, which holds that people should choose actions which conform to a prescribed list of moral rules, and virtue ethics, which holds that people should be judged by how virtuous they are, instead of by what actions they take.
Consequentialism is often associated with maximizing the expected value of a utility function. However, it has been argued that consequentialism is not the same thing as having a utility function because it is possible to evaluate actions based on their consequences without obeying the von Neuman-Morgenstern axioms necessary for having a utility function, and because utility functions can also be used to implement moral theories similar to deontology.
Jeremy Bentham (1907). An Introduction to the Principles of Morals and Legislation. Library of Economics and Liberty.
Perter Fishburn (1970). Utility Theory for Decision Making. Huntington, NY.
Walter Sinnot-Armstrong (2011). “Consequentialism”. The Stanford Encyclopedia of Philosophy (Winter 2011 Edition).
Judith Jarvis Thonson (1975). “Killing, Letting Die, and the Trolley Problem”. The Monist 59: 204-217.