Syntactic Theory

θ Theta Theory θ


Imagine you are writing a screen play. First of all you need a story and various characters, who play different roles in the course of the play. Each role fulfills a special function, so that the story makes sense as a whole.
Grammatical sentences function similarly. Each sentence is an attempt to convey a certain idea or piece of information. In order to do that, each argument has to play a thematic role in the sentence.
The main actors in the play are most likely the subjects and the objects, who typically play the agent and the patient. The co-stars play roles like theme, experiencer, goal, benefactive, source, instrument and locative. So if you want to be a good screenplay writer you have to know your Grammar...


In government and binding theory the theta criterion states that in any grammatical sentence each argument must be assigned to one theta role and each theta role must be realized by some argument. Consequently in a grammatical sentence all predicates, meaning verbs, have a thematic structure. This means that thematic roles, or theta roles (θ-role), describe the relation between predicates and their arguments. As a result arguments stand in different semantic relationships with the verb.


Tobias tells fairytales to his children

4. Theta criterion

  • Each argument is assigned one and only one theta role.
  • Each theta role is assigned to one and only one argument.

Theta roles

  • AGENT: the one who intentionally initiates the action expressed by the predicate.
  • PATIENT: the person or thing undergoing the action expressed by the predicate.
  • THEME: the person or thing moved by the action expressed by the predicate.
  • EXPERIENCER: the entity that experiences some (psychological) state expressed by the predicate.
  • BENEFECTIVE/BENEFICIARY: the entity that benefits from the action expressed by the predicate.
  • GOAL: the entity towards which the activity expressed by the predicate is directed.
  • SOURCE: the entity from which something is moved as a result of the activity expressed by the predicate.
  • LOCATION: the place in which the action or state expressed by the predicate is situated.

(Theta roles according to Haegeman)

A short dialog about theta theory

  • audio version

7. Exercises


Haegeman, Liliane (1994). Introduction to Government and Binding Theory. Blackwell Publishers.