Discuss Case, Thematic roles and Theta theory by citing relevant examples?


Case:  A morphological or Syntactic property of NPs are the Cases in English. It changes according to what a noun, pronoun or adjective does in a sentence. It is a set of forms which depend on the syntactic rules such as movements transformations and agreement.

For Example;

He is an intelligent’, ‘he’ is in Nominative Case because ‘he’ is the subject.

‘John saw him yesterday’, ‘him’ is in Accusative Case, because ‘him’ is the direct object of the verb ‘saw’.

‘This is a house’, ‘this’ is the Possessive Case because there is no notion of possession attached to it.

The main cases in English are;

  • Nominative Case, (The case assumed typically by the subject of a finite clause and the most neutral, least marked among the distinct Case-forms such as; we, she, he, they, are in the Nominative Case)
  • Accusative Case (This is the Case-form of pronouns such as; me, him, them, and thee, it is usually assigned by a verb to its direct or indirect object or by a preposition to its object that is why sometimes it is called as an Objective Case).
  • Genitive Case (The Case taken by a possessor NP, as in his mother, Mr. X’s car etc.

The notions of Thematic Role in Case

Thematic Roles are in a sense closer to the actual meaning of noun phrase than either grammatical function or Cases.

Let’s consider the following sentences;

  • “The door opened” and
  • “The guard opened the door”

In sentence (A) the door acts like a subject, whereas in sentence (B) the door becomes the direct object; therefore, here we can say that the “door” is in thematic role in respect of both sentences. However, NP the guard is the thematic role AGENT who is in real sense performed the action of opening “the door”.

There are several thematic roles such as; EXPERIENCER, INSTRUMENT, GOAL, SOURCE and LOCATION etc.

Case assignment and Case theory

Cases may not necessarily be expressed by means of distinct morphological Case- forms. for example; common noun such as book, cat, dog etc. do not have different case form for Nominative and Accusative forms.

Let’s understand with the help of sentence

  1. That book is interesting to read.
  2. I’ve read that book before.
  3. This cat roams around in the neighbourhood.
  4. Take this cat outside.

In English language it is necessary for NP to have a syntactic case, though it might not express in different form. If NP will not have a case form it won’t be able to connect itself with the sentence. This is what “generative grammarians called “case-filter”. According to generative grammarians ‘Noun Phrase’ is ungrammatical if it is does not have a syntactic case. This term further gives way to another term called “case theory”. This theory ensures that NPs bear meaningful and coherent relationships with the other elements in a sentence, and especially with Case- assigning elements in the sentence. Some of the most crucial syntactic elements of a sentence are Case- assigners. For instance; the verb, assigns Accusative Case to a direct object, only if it is in an active transitive verb and inflection element.

Case Theory is a support of generative grammar which deals with case filter and Case Assignment in a NP or sentence. It is also important in a movement transformational called NP movement.

Case Assignment is a special kind of relationship called government, the head of a phrase governs its Complement and its Specifier as well.

Case and NP movement

Case plays a central role in another salient kind of movement transformation besides ‘Wh’-movement. i.e. NP- MOVEMENT. The Passivization transformation, which derives a passive sentence from a deep structure which is close to its corresponding active sentence in certain respects is now held to be a sub-type of the transformation NP-Movement.

For Example;    (A) ___past + be eaten the mangoes by the children


                                     NP-Movement (Passivization)

                        (B) The mangoes were (= be + past 3 pl.) eaten by the children

In above Case, a passive sentence like in (B) is derived from a deep structure representation that is something like in (A) is the prepositional phrase by the children is in parentheses, which indicate that phrase is optional.

Exceptional Case- Marking (ECM)

Till now we have seen that it is essential for NP to have a syntactic case, but there is certain class of construction where NP is unable to find a syntactic case for itself through usual channel.

For Example;My mother wants [me to go the market]’ In this sentence ‘me’ bears Accusative Case instead of expected Nominative Case. It is an exceptional case marking which is responsible for the Accusative Case of ‘me’.

Thematic Roles

Thematic Role in a linguistic notion, refers as Theta role in syntax or at the syntax- semantic interface. Thematic Roles expresses the role of Noun Phrase that plays with respect to the action or state described by a governing verb. It basically indicates the semantic i.e. meaning (relationship between Noun Phrase and Verb in a sentence).

For Example;

‘Susan ate an apple’ in this sentence ‘Susan’ is the doer of the eating, so she is an AGENT; and the apple is the main item that is eaten, so it is a PATIENT.


Thematic Roles and Theta Theory

These are the parts of the generative grammar that deals exclusively with the thematic roles and often described as Theta theory. It is denoted as θ. Thematic Roles are also known as θ- roles or theta theory. Theta theory is specifically based on Theta Criterion.

Theta Role, a semantic role played by a NP in its capacity is an argument to a verb or preposition or sometimes an adjective like; fond (of) or (worth).

The Lexicon in the generative grammar of a given language is believed to carry S-selection information about the thematic roles required by a given lexicon item.

The Theta theory states that every argument NP must be assigned one and only one thematic role. This also means that every thematic roles must be assigned to one and only one argument. There are basically two thematic roles i.e. AGENT and THEME.

Theta criterion

A criterion or principal states that an argument NP must be assigned one and only one thematic role and conversely. That means every argument NP in a sentence bears one and only one theta role and each theta role is assigned to one and only argument NP.

This criterion ensures that no Noun Phrase is selected by the lexical entry for a given verb or predicate adjective, or even preposition can be in a sentence without being given a proper thematic role.

Thematic Role and Case

It is easy to find a lot of correlation between certain cases and certain thematic roles.

For example; if an argument NP is in a Nominative case, it must be acquire the thematic role of AGENT or EXPERIENCER, and if an argument NP is in a Accusative case, it must acquire the thematic role of THEME or PATIENT. But these correlations the case and thematic role is not always uniform.

An argument NP can have the same thematic role but different case.

For Example; ‘they often like amusing toys’ and ‘Amusing toys are often like by them’. In first, the sentence ‘they’ bears the role of EXPERIENCER and in second ‘them’ bears the role of EXPERIENCER as well, but the cases are different in both the sentences. Therefore, the notion or concept of thematic role or thematic relations plays a significant role in English. Thematic Role are closer to actual meaning of NP than grammatical functions or case are.


Grammatical functions, Cases and thematic roles are often overlapping but not perfectly matching properties that NPs in a sentence display. These functions i.e. Case and thematic roles however, are all possessed by Noun Phrase in a sentence.

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