Peter Singer Tom Regan Gary Francione utilitarian
The two main philosophical approaches to animal ethics are utilitarian and rights-based. The former is exemplified by Peter Singer, and the latter by Tom Regan and Gary Francione. Their differences reflect a distinction philosophers draw between ethical theories that judge the rightness of an act by its consequences (consequentialism/teleological ethics, or utilitarianism), and those that focus on the principle behind the act, almost regardless of consequences (deontological ethics). Deontologists argue that there are acts we should never perform, even if failing to do so entails a worse outcome.
