What is the difference between a thematic role and a grammatical relation?

A thematic role is semantic (who does what to whom), while a grammatical relation such as subject is syntactic. The agent is often the subject, but not always: in a passive the agent is not the subject, showing the two are distinct.

Why are thematic roles hard to count?

Linguists disagree on how fine-grained the inventory should be, since roles like theme and patient overlap and verbs impose subtle distinctions. This difficulty motivated proposals to replace discrete roles with proto-role clusters.

Thematic Roles

Thematic roles are the semantic relations that arguments bear to their predicate, such as agent, patient, and goal, and they mediate between meaning and syntactic structure.

Definition

A thematic role is the semantic relationship an argument bears to the event or state denoted by its predicate, characterising the participant as, for example, the doer, the affected entity, or the endpoint.

Scope

This topic covers thematic (theta) roles: the standard inventory (agent, patient or theme, experiencer, goal, source, instrument, and others), the principles linking roles to grammatical relations and positions, and the proposal to reduce roles to proto-role entailments. It does not cover grammatical relations, case and agreement, or alignment systems, which are treated in sibling topics.

Core questions

What semantic roles do arguments bear to their predicates?
How do thematic roles map onto grammatical relations and syntactic positions?
Is there a fixed inventory of discrete roles, or are roles graded clusters of properties?
How are thematic roles licensed and assigned within the clause?

Key concepts

agent
patient and theme
experiencer
goal and source
theta role assignment
proto-roles
linking rules

Key theories

Case Grammar and deep cases: Fillmore's proposal that clauses are organised around a set of universal semantic roles (deep cases) such as Agentive and Objective, which underlie surface grammatical relations.
Thematic proto-roles: Dowty's account replacing discrete roles with two cluster concepts, Proto-Agent and Proto-Patient, defined by entailments; argument selection follows from which argument has more proto-agent or proto-patient properties.

History

Thematic roles trace to Gruber's and Fillmore's (1968) Case Grammar, which posited semantic roles underlying syntax. Generative theory incorporated theta roles and the Theta Criterion, requiring a one-to-one assignment of roles to arguments. Dowty (1991) argued that discrete roles should give way to two proto-role clusters defined by entailments, reframing how arguments are selected for grammatical relations.

Debates

Discrete roles versus proto-roles: Whether arguments bear a fixed set of discrete thematic roles or are characterised by graded proto-agent and proto-patient entailments, with the latter avoiding problems of role individuation.

Key figures

Charles Fillmore
David Dowty
Jeffrey Gruber
Andrew Carnie

Seminal works

fillmore1968
dowty1991
carnie2013

Frequently asked questions

What is the difference between a thematic role and a grammatical relation?: A thematic role is semantic (who does what to whom), while a grammatical relation such as subject is syntactic. The agent is often the subject, but not always: in a passive the agent is not the subject, showing the two are distinct.
Why are thematic roles hard to count?: Linguists disagree on how fine-grained the inventory should be, since roles like theme and patient overlap and verbs impose subtle distinctions. This difficulty motivated proposals to replace discrete roles with proto-role clusters.