One of the most controversial topics today is the definition of a person. While few people recognize this as key to many issues, it is at the heart of our legislation and moral beliefs. The question answers for many whether abortion is murder, whether individuals who have sustained higher and whole brain death are already dead, whether computers can be people, and whether animals should have rights. The definition is not clear cut.

Many contemporary philosophers interpret René Descartes’ famous quote "Cogito ergo sum" as his definition of a person. According to these philosophers’ beliefs, a person is one who can think that they are thinking, something they define as consciousness. According to this, an individual who has suffered high or whole brain death is not a person, and hence taking them off "life-support" would not be murder. Since a fetus lacks consciousness, killing it would not be murder. Also, a human with little mental capacity, as is common with mental retardation, would not be a person.

Opponents from the religious right often use a far different definition of a person. Their definition states that a person is a human from the time they are conceived to the time their hearts stop beating permanently. This definition would then include a brain dead human on "life-support", and a fetus the second after conception. Once this definition is applied to legislation, it becomes quite clear that it is far more emotional than logical. A body that has suffered higher brain death may continue to function for years without any benefit to that individual or those taking care of it. Since they have to be constantly monitored to keep from swallowing their tongues, be cleaned every few days, and have nutrition tubes supply them with food, expenses for attending to those individuals average $120,000 per year. If socialized medicine is instituted, the expenses to keep these corpses from decomposing fall on everyone's shoulders.

A popular adage associated with animal right activism is "Animals are people, too." This adage derives from the fact that the definition of a person is ambiguous. Peter Singer writes in his essay "All Animals are Equal", "From the mere fact that a person is black, or a woman, we cannot infer anything else about that person." Accordingly, simply because an individual is human doesn't necessitate any level of intelligence. In fact, the intelligence level of some great apes far exceeds the level of some humans, i.e., those who have suffered brain damage or those who are mentally retarded. With such diverse applications of the word person, which is generally used when referring to humans, a strong argument can be made to include non-human animals. Clearly, if animals are to be considered persons, they should be granted rights fitting for them, and hence should not be subjected to cruel animal testing.

Given the advancement of computers these past few decades, androids are a clear possibility. Today, neural networking is the field that develops a computerized approximation of the human brain. Today, we see this applied to voice and handwriting recognition. Already computers are able to create things on their own. Some are no longer just what the programmer enters into them. They already fit the Cartesian definition of a person. They are able to report that they are processing information and the speed at which they are processing it. Whether some will consider computers to be persons in practice has yet to be determined.