A central concern of liberal political theory is to determine the place of consent in the legitimation of social and political practices. Coercion, exploitation, fraud, deception, and perhaps more general categories of treating people as means, all imply a lack of someone's consent to what has happened. Conversely, just or permissible transactions imply either the actual or potential consent of affected parties. In order to remove the obvious problem that a person may be bound by the laws of a country when there has been no episode of actual consent, a doctrine of tacit consent was developed by Locke. More common now is a concept of potential consent, that is, of a situation being such that an appropriately placed subject would or could rationally consent to it. It is possible to envisage the entire moral and political framework built upon the idea of those interactions to which a person could rationally consent, although the development of this theme requires a view of the motivations as well as the knowledge, rationality, and situation of the agent. See also contractarianism, Rawls.