A person is a thing that can act, move, speak, and be held responsible. People are the things that do things on purpose. A rock sits where it is. A person walks somewhere because they want to go there.

A person is an object — they have mass, take up space, exist physically. A person is mobile — they move between areas under their own power. But a person is more than a mobile object. A person has agency: they choose, they communicate, they make promises, they break them. A cart is mobile but not a person. A robot that moves is mobile but arguable. A sleeping human is still a person — agency is a capacity, not a continuous activity.

Persons occupy containers. A person is in a room, on a ship, at a workstation. Like any object, a person has a location at any given moment. Unlike most objects, a person changes location by deciding to. The move operation in TAB works on any mobile, but for persons the move is volitional — they go somewhere because they choose to, not because someone carried them.

Persons can receive messages. In TAB, when something happens in a container, the container broadcasts to its contents: “The door opens.” “An apple arrives.” Only things that can receive messages — persons, primarily — actually process those messages. Objects just sit there. Persons notice, react, respond.

Persons can hold, carry, and use objects. A person picks up a cup, puts on a coat, swings a hammer. The relationship between person and object is asymmetric — the person acts on the object, not the other way around. Tools extend what a person can do, but the person is the one doing.

Persons have grammar. TAB gives every thing pronouns, but for persons the pronouns matter socially: he, she, they, I, you. A person is addressed in the second person and refers to themselves in the first. No other kind of thing does this. Language is built around the assumption that some things in the world are persons and the rest are not.