The question: What is a person? is more complex than it appears. Indeed, when we recognize the complexity of the question, and forget our assumption that a person should be a human being. We can no longer thing of a picture of homo sapiens, Vitruvian Man or his slightly obese contemporary counterpart, so the concept of a “person” becomes enigmatic.
What about: the bearer of something? The bearer of free will, or rights, or responsibilities? But this is begging the question. A person is recognized as a person when he is considered the bearer of these dignities. Francis Fukuyama writes about this in his recent book on “Identity”, following Hegel that history is the dialectical play of recognition, resulting in the liberal democratic society at the famous “end” of history. Philosophy in this sense is translating common sense into notions, not investigating some underlying substance.
Such “substance” is the domain of metaphysics and it seems dangerous to let that discipline decide what (who!) counts as a person and who doesn’t. This theoretical question will become extremely relevant of course in the impending era of artificial intelligence. As soon as “chatbots” portray the characteristics of personhood and manage to obfuscate the algorithmic origin of their utterance, we can expect action groups advocating a bill of rights for these computer programs. The right to live, for example, translates into a right not to be shut down.
Machines have to pass the Turing test, or generate enough doubt so we have to assume they could pass, in order to be considered persons. The ability to have a human-like conversation appears to be the only criterion for personhood. This seems to excludes other animals. I would argue that we should be as benevolent as we could be in our interpretation of what we count as a conversation. We talk to our companion animals or pets, and there sure is mutual understanding. Some animals also partake in the life of the mind. And just to be on the safe side, why don’t we include them all and assign them some sense of personhood, and a right to life, dignity and the pursuit of happiness?
Judging if we are dealing with a person becomes the responsible task of other persons, in which they give their best effort to discern symptoms of personhood. We are generous with personhood.