A person is a being, such as a human, that has certain capacities or attributes constituting personhood, which in turn is defined differently by different authors in different disciplines, and by different cultures in different times and places.
In addition to the question of personhood, of what makes a being count as a person to begin with, there are further questions about personal identity and self: both about what makes any particular person that particular person instead of another, and about what makes a person at one time the same person as he or she was or will be at another time despite any intervening changes.
Development of the concept
In ancient Rome, the word persona (Latin) or prosopon (πρόσωπον; Greek) originally referred to the masks worn by actors on stage. The various masks represented the various "personae" in the stage play.
The concept of person was further developed during the Trinitarian and Christological debates of the 4th and 5th centuries in contrast to the word nature. During the theological debates, some philosophical tools (concepts) were needed so that the debates could be held on common basis to all theological schools. The purpose of the debate was to establish the relation, similarities and differences between the Λóγος/Verbum and God. The philosophical concept of person arose, taking the word "prosopon" (πρόσωπον) from the Greek theatre. Therefore, Christus (the Λóγος/Verbum) and God were defined as different "persons". This concept was applied later to the Holy Ghost, the angels and to all human beings.
Since then, a number of important changes to the word's meaning and use have taken place, and attempts have been made to redefine the word with varying degrees of adoption and influence.
Personhood is the status of being a person. Defining personhood is a controversial topic in philosophy and law, and is closely tied to legal and political concepts of citizenship, equality, and liberty. According to law, only a natural person or legal personality has rights, protections, privileges, responsibilities, and legal liability. Personhood continues to be a topic of international debate, and has been questioned during the abolition of slavery and the fight for women's rights, in debates about abortion, fetal rights, and in animal rights advocacy.
Various debates have focused on questions about the personhood of different classes of entities. Historically, the personhood of animals, women, and slaves has been a catalyst of social upheaval. In most societies today, living adult humans are usually considered persons, but depending on the context, theory or definition, the category of "person" may be taken to include or not children or such non-human entities as animals, artificial intelligences, or extraterrestrial life, as well as legal entities such as corporations, sovereign states and other polities, or estates in probate.
The category may exclude some human entities in prenatal development, and those with extreme mental impairment.
Personal identity is the unique identity of persons through time. That is to say, the necessary and sufficient conditions under which a person at one time and a person at another time can be said to be the same person, persisting through time. In the modern philosophy of mind, this concept of personal identity is sometimes referred to as the diachronic problem of personal identity. The synchronic problem is grounded in the question of what features or traits characterize a given person at one time.
Identity is an issue for both continental philosophy and analytic philosophy. A key question in continental philosophy is in what sense we can maintain the modern conception of identity, while realizing many of our prior assumptions about the world are incorrect.
Proposed solutions to the problem of personal identity include: continuity of the physical body, continuity of an immaterial mind or soul, continuity of consciousness or memory, the bundle theory of self, continuity of personality after the death of the physical body, and proposals that there are actually no persons or selves which persist over time at all.