Jonathan Wolff

Hobbes Lecture: 13/3/03

Prisoners’ Dilemma

Two prisoners are each questioned by the police, who have evidence to convict them both of a minor charge. But they have also together committed a major offence for which the police have no admissible evidence. Each is taken to a separate cell. Prisoner A is told that if neither confess they will each get one year in prison. But if he confesses to the major crime and prisoner B does not he will be let off and B will get 10 years. Conversely if A doesn’t confess and B does A get 10 years and B will get off free. If they both confess they will both get 5 years.

Suppose they are rational and entirely self-interested. What will happen?

A will argue that if B doesn’t confess, then it is better for A to confess (that way he gets off). But if B does confess then it is better for A to confess too, otherwise he gets 10 years instead of 5. So whatever B does it is better for A to confess. So A will confess. B reasons in exactly the same way. So they both confess. So they both get 5 years. But if neither confesses they both get 1 year.

	B not confess	B confess
A not confess	1 year each	A=10, B=0
A confess	A = 0, B=10	5 years each

Question: Is Hobbes’ state of nature a prisoners’ dilemma?

Distinguish

a) One shot and multi play

b) Two person and multi person