"Portraits and Persons" by Cynthia Freeland is a welcome addition to our conversations. Before, reading this post, ask yourself what attributes define a portrait for you? I'd be happy to post your comments/replies.
Ms. Freeland, a philosophy professor and author of an earlier book "But, is it Art?", dove into this topic and exercised every angle of the definition of portraiture including what or who can be the subject of a portrait.
To be a portrait, she claims the following must be present in the depiction: "A recognizable physical body along with an inner life and the ability to pose or present oneself to be depicted in a representation."
The book solidly supports these points and even handles the question of pets and animals. She also illustrates that portraits can fulfill some important functions: "providing a likeness, phycological characterizations, proofs of presence or 'contact' and manifestations of a person's essence." But, don't take my word for it ... read the book.