The experience of pain is something that most people are extremely familiar with. However, once we begin to examine the subject from an ethical point of view, and particularly when we examine so-called marginal cases such as nonhuman animals, we are quickly confronted with difficult questions. This thesis, through an examination of a particular feature of moral language and a description of recent research on pain, provides an analysis of how pain fits into ethical theory. It is argued that universalizability is an important feature of ethical systems and provides a basis for claiming that an agent is acting inconsistently if he or she evaluates similar situations differently. Though the additional features prescriptivity and overridingness provide an important connection between moral judgment and action in HareAcA?A?s two-level utilitarianism, it is argued that they ultimately lead to claims incompatible with lived moral experience. Arguments by Parfit and Sidgwick are discussed which tie acting morally to acting consistently, and it is concluded that selfinterest theory is not a tenable position. After the features of moral judgment are discussed, the necessary features of a moral subject are examined. It is concluded that sentience, or the ability to feel pleasure or pain, is a sufficient condition for being a moral subject. Arguments are examined that attempt to show which animals likely consciously experience pain. Difficulties for these arguments are discussed and an original argument is presented that at least partially addresses these difficulties. It is concluded that from an ethical perspective our current practices such as factory farming are probably not justified. It appears especially likely that our treatment of other mammals is unethical, but the answers are not as clear with other animals. However, all of the conclusions are tentative, as no doubt future scientific investigation will shed more light on our knowledge.
