The common means of defining which individuals should receive this right to non-exploitation--skin color, gender, nationality, etc.--are all indefensible and morally irrelevant prejudices. There must be a rational and consistent means of determining whether an object should receive this right (my daughter) or should not (a rock).
Many different criteria for deserving rights have been put forth, including intelligence, potential, ability to enter into moral contracts, the law, appearance, and value to others. The first three sound reasonable, but are not inclusive enough to be workable, for infants and irreversibly brain-damaged human beings would not be granted rights in these scenarios. The law, like religious doctrines, changes over time: e.g., slavery finally became illegal and out of favor with the church. Appearance has been the dividing line in the past (if a person looks like me, then they deserve rights), but this bias does not separate my daughter from a mannequin.
The concept of value to others is put forth by those who want to include infants and irreversibly brain-damaged human beings in the circle of the rights-deserving while excluding other animals. By this argument, infants themselves do not possess any inherent rights, but receive them only if valued by an adult human. Yet being valued by an adult human does not grant rights to pigs, parakeets, pet rocks, or Porsches. Most people would contend that even unvalued orphans have inherent rights. Therefore, rights must be based on other criteria.
Others would argue that people have rights if they belong to the species Homo Sapiens. However, the questions then become: Why should rights be deserved solely on the basis of a certain sequence of genes? If rights should be based on genes, why should the line be drawn at the species level and not at gender, race, order, phylum, or kingdom? Among the genes that determine eye color, gender, etc., which gene is it that confers rights?
It is this latter point that confuses many in our society who think that even one cell with a unique (Homo Sapiens) genetic code deserves the same rights as an adult. However, most people believe that a cancer cell--mutated such that its genetic code is unique but still Homo Sapiens--does not deserve rights. A thoughtful person might find having their rights (or lack thereof) determined by a sequence of atoms to be a bit absurd. It is no better than basing rights on the pigmentation of one's skin (which is also determined by the individual's genetic code).
To have a consistent moral philosophy, a morally relevant characteristic must be found that not only allows for the inclusion of all humans, but also distinguishes between a wax dummy and an infant. The only characteristic that simply and consistently meets these requirements is the capacity for suffering. As Jeremy Bentham, head of the Department of Jurisprudence at Oxford University during the 19th Century said in reference to his belief that not only white human males should be granted rights: "The question is not, 'Can they reason?' Nor, 'Can they talk?' But rather, 'Can they suffer?'"
If a being cannot suffer, then it does not matter to that being what happens to it. For example, some computers have an intelligence (in many ways greater than any human), but these machines do not care whether they are turned off, harmed, or even destroyed. On the other hand, if a being is sentient--able to actively experience pleasure and pain--then it does matter to that being what happens to it. All sentient beings deserve to have their interests and inherent value respected. Any complete moral philosophy cannot ignore these concerns.
Vegan Outreach Homepage on the World-Wide Web.