clear and therefore controversial. The contradictory impulses have resulted in a situation where most theories of grammar acknowledge the grammatical relations and rely on them heavily for describing phenomena of grammar but at the same time, avoid providing concrete definitions of them. Nevertheless, various principles can be acknowledged that attempts to define the grammatical relations are based on. Thematic criteria The thematic relations (also known as thematic roles, and semantic roles, e.g. agent, patient, theme, goal) can provide semantic orientation for defining the grammatical relations. There is a tendency for subjects to be agents and objects to be patients or themes. However, the thematic relations cannot be substituted for the grammatical relations, nor vice versa. This point is evident with the active-passive diathesis and ergative verbs: Marge has fixed the coffee table. The coffee table has been fixed (by Marge). The torpedo sank the ship. The ship sank. Marge is the agent in the first pair of sentences because she initiates and carries out the action of fixing, and the coffee table is the patient in both because it is acted upon in both sentences. In contrast, the subject and direct object are not consistent across the two sentences. The subject is the agent Marge in the first sentence and the patient The coffee table in the second sentence. The direct object is the patient the coffee table in the first sentence, and there is no direct object in the second sentence. The situation is similar with the ergative verb sunk/sink in the second pair of sentences. The noun phrase the ship is the patient in both sentences, although it is the object in the first of the two and the subject in the second. The grammatical relations belong to the level of surface syntax, whereas the thematic relations reside on a deeper semantic level. If, however, the correspondences across these levels are acknowledged, then the thematic relations can be seen as providing prototypical thematic traits for defining the grammatical relations. Configurational criteria Another prominent means used to define the syntactic relations is in terms of the syntactic configuration. The subject is defined as the verb argument that appears outside of the canonical finite verb phrase, whereas the object is taken to be the verb argument that appears inside the verb phrase. This approach takes the configuration as primitive, whereby the grammatical relations are then derived from the configuration. This