 MacCallum defines the basic concept of freedom — the concept on which everyone agrees — as follows: a subject, or agent, is free from certain constraints, or preventing conditions, to do or become certain things. Freedom is therefore a triadic relation — that is, a relation between three things: an agent, certain preventing conditions, and certain doings or becomings of the agent. Any statement about freedom or unfreedom can be translated into a statement of the above form by specifying what is free or unfree, from what it is free or unfree, and what it is free or unfree to do or become. Any claim about the presence or absence of freedom in a given situation will therefore make certain assumptions about what counts as an agent, what counts as a constraint or limitation on freedom, and what counts as a purpose that the agent can be described as either free or unfree to carry out.