Thematic Relation - Conflicting Terminologies

Conflicting Terminologies

The term "thematic relation" is frequently confused with theta role. Many linguists (particularly generative grammarians) use the terms interchangeably. This is because theta roles are typically named by the most prominent thematic relation that they are associated with. To make matters more confusing, depending upon which theoretical approach one assumes, the grammatical relations of subject and object, etc., are often closely tied to the semantic relations. For example, in the typological tradition agents/actors are tied closely to the notion of subject (S). Here is a way to distinguish these ideas, when they are used distinctly:

• Thematic relations are purely semantic descriptions of the way in which the entities described by the noun phrase are functioning with respect to the meaning of the action described by the verb. A noun may bear more than one thematic relation. Almost every noun phrase bears at least one thematic relation (the exception are expletives). Thematic relations on a noun are identical in sentences that are paraphrases of one another.
• Theta roles are syntactic structures reflecting positions in the argument structure of the verb they are associated with. A noun may only bear one theta role. Only arguments bear theta roles. Adjuncts do not bear theta roles.
• Grammatical relations express the surface position (in languages like English) or case (in languages like Latin) that a noun phrase bears in the sentence.

Thematic relations concern the nature of the relationship between the meaning of the verb and the meaning of the noun. Theta roles are about the number of arguments that a verb requires (which is a purely syntactic notion). Theta roles are a syntactic relation that refers to the semantic thematic relations.

For example, take the sentence "Reggie gave the kibble to Fergus on Friday."

• Thematic relations: "Reggie" is doing the action so is the agent, but he is also the source of the kibble (note Reggie bears two thematic relations!); "the kibble" is the entity acted upon so it is the patient; Fergus is the direction/goal or recipient of the giving. Friday represents the time of the action.
• theta roles: The verb "give" requires three arguments (see valency). In generative grammar, this is encoded in terms of the number and type of theta roles the verb takes. The theta role is named by the most prominent thematic relation associated with it. So the three required arguments bear the theta roles (confusingly!) named the agent (Reggie) the patient (or theme) (the kibble), and goal/recipient (Fergus). "On Friday" does not receive a theta role from the verb, because it is an adjunct. Note that "Reggie" bears two thematic relations (Agent and Source), but only one theta role (the argument slot associated with these thematic relations).
• grammatical relations: The subject (S) of this sentence is "Reggie", the object (O) is "the kibble", the indirect object is "to Fergus", and "on Friday" is an oblique.