Theta Roles

Linguistics 322/481

Intermediate Syntax


Contents: Theme | Locative | Experiencer | Agent | Wormhole | Experiencer versus agent | Instrument | Possessor | Patient | Constructum | Destructum | Trigger | Location | Goal, Source, and Path | Reason | Purpose | Benefactor | Wormhole Revisited

Theta roles are the names of the participant roles associated with a predicate: the predicate may be a verb, an adjective, a preposition, or a noun. The participant is usually said to be an argument of the predicate.


If an object is in motion or in a steady state as the speakers perceives the state, or it is the topic of discussion, it is called a theme:

(1)     The book is blue.

(2)     The ball rolled away.

(3)     Did you see Molly?

In (1) the book is the theme, in (2) the ball is the theme, and in (3), Molly is the theme. In the latter case Molly is the topic of conversation; you is an experiencer. The theme does not imply a information processing unit (IPU)--see next two sections.

(4)    [TENSE [-Past] < BLUE <theme: BOOK> >].

(5)    [TENSE [+Past] < ROLL <theme: BALL> <source: AWAY> >].

(6)    [TENSE [+Past] < SEE <theme: MOLLY> <experiencer: YOU> >].

The default position for the theme is the complement of V0 or A0--the internal argument position:

(7)     [VP [Vo SEE [NP MOLLY]]]

(8)    [AP [Ao BLUE [NP THE BOOK]]]

(9)    [VP [Vo ROLL [NP THE BALL]]]

We will deal with "away" later. In (8) and (9), The internal argument is targeted since there is no external argument:



Location is a theta role that marks the stationary position of an object in resplect to some other object:

(11)   The book is on the table.

(12)   Tilly's car is in the garage.

(13)   The sun lies within the earth's orbit.

In (64) the table is a location; the book is a theme. Location is often headed by a preposition; that is, it is an argument of the verb. However, location can be an argument of a verb:

(14)   The punch is inthe punchbowl.

(15)   The punchbowl contains the punch.

The near synonymy of (14) and (15) provides evidence that punchbowl is a location in (14), and that punch is a theme, just as in (15).

Locative is assigned to the internal argument of P; the theme is assigned to the argument position which is a sister to P1. The L-Structure of (11) is given:



In the following sentence, John is the argument of die. John is a participant; he is the one who dies. If one undergoes an experience denoted by the verb, the theta-role is called an experiencer:

(17)     John died.

Here, John has experienced death. We may represent this argument in propositional form:

(18)    [TENSE [+Past] < DIE <experiencer: JOHN>>].

If there is no theme as in (1) directly above the experiencer is assigned to the internal argument positon. If there is a theme, by the default rule, the theme occurs in the internal argument position and the experiencer occurs in the external argument position:

(19)    John likes Mary.

"John" is the experiencer. "Mary" may or may not be the theme, depending on one's analysis of thea-roles. Let "Mary" be the theme for the time being.In the active voice the external argument is targeted, and in the passive voice the internal argument is targeted:

(4)     Mary is liked by John.

In the semantically close AP "be pleased", the theme is targeted for prominence, while the experiencer occupies the goal position (see below).


If the participant is causing something to happen or is in some way responsible for something happening or has conscious control over something happening, the participant is called an agent:

(9)     Bill is building a house.

(10)     Mary bought a beat up car.

(11)     The dog is running away.

The subject in each of these sentences is an agent. The progressive aspect is not represented in the following grammatical propositional forms:

(12)    [TENSE [-Past] < BUILD <goal: HOUSE> <agent: BILL> >].

(13)    [TENSE [+Past] < BUY <theme: CAR> <agent: MARY> >].

(14)    [TENSE [-Past] < RUN <agent: DOG> <source: AWAY> >].

We claim here that an agent deals with the submission of information. The agent sends out information to a certain form that is responsible for causing an event to occur. The immediate source of this information we will call an Information Processing Unit (IPU). We will look at three different scenarios.

In all natural languages, the agent seems to be assigned to the external argument position without exception:

(15)     [VP [V1 [Vo BUILD ] [NP HOUSE ]] JOHN ].

The Wormhole Example

Wormhole (1)


Nevertheless, the three scenarios are the same. Each movable form has an IPU that sends out one bit of information to some form that is the direct cause of movement. The IPU is the agent. In normal language, we refer to the entire body containing the IPU as the agent:

(15)     The human crawls through the wormhole.

As long as the human brain functions and sends information to the hands and feet, we say that the human is the agent as in (15). The human body is the theme of the motion, not the brain. The brain is a theme in respect to the worm: it is located inside the worm. Note that in (4) the subject is not an agent. The subject we discuss in the following section.

Agent versus Experiencer

To explain agent and experiencer, let us start with the following scenario. Imagine a wormhole that is straight and has two ends. Next imagine that there is a worm that moves through the wormhole from one end to the other. But when it reaches the end, it can no longer move. Suppose next that the worm has an information processing unit (IPU) (or a CPU (a central processing unit)). This IPU we may call the brain of the worm. The worm also has two sensors, one at each end of his body. When the worm comes into contact with the end wall of the wormhole, the sensor at the point of contact picks up this information and sends the information to the IPU of the worm (through his neural system). Now imagine that the worm is now able to send one of two messages to its body. Move and Reverse Movement. When the worm receives the information that it has reached the end of the wormhole, it send the message to its body to reverse the direction, and then it send out the message to move. When the worm reaches the other end of the wormhole, the same process is repeated.

We will call the IPU an experiencer when it receives information and an agent when it submits information. The body of the worm is still a theme. Technically the sensor acts as an experiencer when it senses the end of the wormhole, and as an agent when this information is passed to the IPU. Thus, we now have several events:

  1. MOVE <theme: WORM>
  2. REACH <goal: END-of-WORMHOLE> <agent/theme: WORM> = INFORMATION-1
  3. TOUCH <theme: END-of-WORMHOLE>
  4. ACTIVATE < experiencer: SENSOR>
  5. TRANSMIT <theme: INFORMATION-1> <goal: IPU> <agent: SENSOR>
  6. RECEIVE <experiencer: IPU> <theme: INFORMATION-1>
  7. PROCESS <agent: IPU> <theme: INFORMATION-1>
  9. TRANSMIT <theme: INFORMATION-3> <goal: ORGANS-of-MOVEMENT> <agent: IPU>
  10. MOVE <theme: WORM>.
  11. [Repeat].

INFORMATION-1 is the reaching of the end of the wormhole, INFORMATION-2 is to change direction, and INFORMATION-3 is to move. This chain of events will repeat endlessly without any further information brought in. Even if the worm should die, that is additional information.

Every term that is in caps is called a predicate. Certain predicates are events and certain ones objects. The objects appears as arguments of one or more events.

The experiencer is distinct from the agent. It is possible for the IPU to receive information and not respond to it. For example, consider:

(16)     John felt cold.

(16) is ambiguous. In the intended reading John is experiencing being cold. John is the experiencer. Something is sending him the information that he is experiencing this condition. But in (18) John is doing nothing about it. John is an experiencer only in (17). In the second reading, John feels cold to the touch. That is someone else is experiencing John's coldness. John's body is cold. We do not know if John is experiencing being cold or not. John could be dead, in which case his IPU (brain) is not function and it is neither receiving messages or submitting messages (tense and other verbal operators are ignored here):

(17)     FEEL <experiencer: JOHN> <[STATE] COLD>>.

(18)     FEEL <[STATE] <COLD <theme: JOHN> <experiencer: X> .

(18) is more complex that what I have written. John is experiencing the state of being cold. Semantically, John has the be the experiencer of feeling cold, and he has to be in the state of being cold. In the argument structure only one of the arguments with an identical referent appears. We assume the subject of the sentence to be the argument of FEEL--the experiencer. In (16) an experiencer is implied, but not stated, though it can be as in (19):

(19)     John felt cold to the mortician.

Normally, we perceive of animals and humans as experiencers but not computers. The computer is an experiencer in the following situation. When the minicomputer reaches the end bumping into it, a message is sent to the IPU of the computer that the end has been reached. The computer then sends out a message to some mechanism (an instrument) that reverses the direction of it. Then the computer sends out the message 'Move.' Perhaps the difference between animals and computers is that the former have free will, but the latter do not except in science fiction situations such the computer Hal.

In the following sentence:

(20)     John saw Mary.

seeing is an experiential event. The seer is receiving information: the object seen. The object seen is the theme. The seer is not sending out information--he is not an agent. (Perhaps in a more technical sense, the object seen is the source; the information passed to the brain is the theme. I do not think it is necessary to go into this level of detail here.)


Let us suppose that this particular species of worm has teeth. When the worm reaches the end of the wormhole, it receives that message, and then it sends a message to the tooth muscles (or whatever) to bite into the end, tear off a bit of the end, and then consume it. The teeth and associated organs are an instrument (perceptually, we humans often see the teeth as the instrument, passing over the muscles involved):

(21)     The worm ate a bit of the wormhole end with its teeth.
(22)    [TENSE [+Past] < EAT <theme: BIT of WORMHOLE END> <instrument: TEETH> >].

The instrument has no IPU. It receives a message, but it cannot process it. If the message comes in, the teeth must sink into the end of the wormhole. In this way we distinguish between agent and instrument. In a sentence such as:

(23)    The wind blew down the tree,
(24)    [TENSE [+Past] < BLOW <theme: TREE> <position-goal: DOWN> <instrument WIND>].

it is assumed that the wind has no IPU. If true, then the wind is an instrument, not an agent. It has been noted in the literature that the following sentence is ambiguous:

(25)     Bill broke the window.
(26)     [TENSE [+Past] < BREAK <patient: WINDOW> <agent: BILL>].
(27)     [TENSE [+Past] < BREAK <patient: WINDOW> <instrument: BILL>].

In one reading Bill is the agent. In the other (uncommon) reading, Bill's body is an instrument in that somehow it went through the window, but Bill had nothing to do with it. Bill did not send out a message to some part of his body to propel his body through the window. Or, Bill broke the window when he fell through it.

Bill is an instrument here unless he intentionally fell through the window with the intent of breaking it. The instrument occurs as the direct object of the verb use:

(28)    Seymour sliced the salami with a knife.
(29)    Seymour used a knife to slice the salami.
(30)    John used a rock to beat the window.
(31)    Mary used a colander to drain the spaghetti noodles.
(32)    The worm used his teeth to chew of a bit of the wormhole.

Returning to the wormhole example, the organs of movement are each an instrument:

(33)    The worm moves through the wormhole with its organs of movement.
(34)   The worm uses its organs of movement to move through the wormhole.

Ignoring for the moment through the wormhole; the proposition structure for (33) is the following:

(35)     [TENSE [-Past] < MOVE <agent: WORM> <instrument: ITS ORGANS OF MOVEMENT>].

These organs do not have an IPU. Therefore, they can function neither as an agent or an experiencer. But they can function as an instrument. Sometimes an object can function as an agent or an instrument:

(36)  John broke the window with a hammer.
(37) John broke the window when he was thrown through it.

In (36) hammer is the instrument since it has no IPU, and John is the agent since he uses his IPU to make arms and various organs to cause the hammer to break the window. In (37) John is not an agent but an instrument. John's IPU has nothing directly to do with his body being thrown through the window. Sentence (38) is ambiguous:

(38)   John broke the window when he fell through it.

If John accidentally fell through the window, he is a theme as long as he did nothing to cause himself to fall through the window. If John intentionally fell through it, he an agent, and if his intention was to use his body to break the window, then he (his body) is an instrument.


The theta role possessor refers to an object that one has, owns, possesses, or belongs to someone:

(38)    John has a book.

Book must be a theme. It sends out no messages and it receives no messages, and it does not undergo a change of state (see patient below):

(39)     [TENSE [-Past] < HAVE <possessor: JOHN> <theme: <BOOK> >].

Let's return to the worm hole:

(40)     The worm has two sensors.

(41) He has four organs of movement and an IPU.

Thus, the worm is a possessor, what he possesses are themes.


Another common theta role is the patient. The patient is something or somebody that undergoes a change specifically implied by the verb. Note that John in (1) is a also a patient in that he underwent a change in state. Other patients include:

(42)      Mary burned the scallops.

(43)      Kelly painted the fence.

In (23) the scallops is the patient, since it underwent a change; in (24) the fence is a patient since it underwent a change (in colour). A patient occurs in the following slot:

(44)     What did X do to the ______ ?
(45)     What did Mary do to the scallops? She burned them.
(46)     What did Kelly do to the fence? He painted it.

In the above wormhole scenario there is no patient. There does not undergo an observable internal change. Suppose that the worm has a mouth and can eat a bit of the end of the wormhole and then reverses his direction. As a result of eating a bit of the end of the wormhole, the worm grows a millimeter. The worms is a patient in the sentence:

(47)     The worm grew an inch.

Of course, the worm is an agent in

(48)     The worm ate a bit of the wormhole end.

And the wormhole end is also a patient. Note that the verb eat does not refer directly to an experience. The experience is inferred. When the worm reaches the end of the wormhole, it receives the information that it has reached the end, and then the worm sends out information to the proper organ to eat a bit of the end.

Note that in the depiction of the wormhole given above, there is no patient. The worm does not undergo a change of state.


The theta role result is not a commonly recognized theta role. It refers to object that come into existence as a consequence of the assigning predicate. Consider the following sentences:

(49) John baked a cake.

(50) Mary built a coffee table.

(51) Mrs. Jones created a mess.

(52) Noah constructed a huge ark.

The objects cake, coffee table, mess, and huge ark are the result of doing something. These objects did not exist before the time point of the event, but only after it and as a result of it. In some sense this is related to goal.


The theta role destructum is not known to have been proposed. It refers to objects that cease to exist as such as a consequence of the assigning predicate. Consider the following sentences.:

(53) The enemy destroyed the city.

(54) Some Doukhobor burned his house down.

(55) A tornado leveled the town.

(56) Jimmy Hoffa was rubbed out.

The city, his house, the town, Jommy Hoffa are destructa, since they no longer exist.


Differentiating between instrument and trigger is somewhat difficult. The trigger (perceptually) is what actually triggers an activity or accomplishment. An instrument is an aid and is more closely associated with the action (if external) than the subject, but trigger is not an aid. Trigger is often marked by a PP whose had is from:

(57) John died from the poison.

(58) Mary got sick from the improperly cooked food.

(59) My bother's arm became swollen from the mosquito bite.

(60) Bill's dog got sick from eating too much food.

In () the poison is not an instrument since it is not necessarily the case that someone used it to to poison John. John could have accidentally eaten something contaminated with the poison. Compare () with:

(61) Mary killed John with the poison.

(62) *Mary killed John from the poison.

(63) *John died with the poison.

In (61) Mary uses the poison as an instrument to kill John. Here poison is an instrument. But note one cannot say (62) where from implies a trigger, not an instrument. And it (63) the verb die cannot take an instrument, only a trigger. Part of the difference between die and kill is that the latter takes an instrument, the former a trigger. Die is an achievement verb, whereas kill is an accomplishment verb.



Goal, Source, Path

Other theta roles include goal, source, and path. The first three occur with events denoting specific motion:

(69)    John walked from school past the burning effigy to the library.
(70)    The ball rolled from the door down the hallway to the kitchen.
(71)    [TENSE [+Past] < <source: SCHOOL> <path: PAST BURNING EFFIGY> <goal:   LIBRARY> <agent: JOHN> >]
(72)    [TENSE [+Past] < <source: DOOR>     <path: DOWN HALLWAY> <goal:            KITCHEN> <theme: BALL> >]

Let us illustrate with the worm. In the simplest scenario, the worm is the agent. No reference had been made to the wormhole. In the following sentence:

(73)   The worm moved through the wormhole.

The wormhole refers to the path of the movement of the worm. The wormhole bears the theta role path. Each end of the wormhole alternatively functions as a source or goal; simulatneously the other end has the oppose thata role. For example, if end one is the goal, end two is the source, and vice versa. The worm just keeps moving. In the second case, there are two ends of the wormhole. The worm moves from one end to the other. Thus, one end is the source, and the other is the goal. Note that without tense, it would be impossible to determine which end is the goal and which is the source. Bring in the factor of tense, the source is the end in the past tense, and the goal is the end in the future:

(74)   The worm moved from one end (source) to the other end (goal).

Some prepositions add an extra level of analysis:

(75)     Sally walked into the room.

Into is a compound preposition. The second part to marks goal, whereas in marks the location:

(76)     <agent: SALLY> WALK <goal: TO <IN <location: ROOM>>

Note that in (77) the goal is marked, but the location is not:

(77)   Sally walked to the room.

(77) does not imply that Sally actually entered the room. Her location is not overt.

Path is marked by several prepositions in English: through, up, down, over, under, next to, besides, around. Some of these prepositions also mark location: over, under, next to, besdies, around.


Another theta role is reason. The English words because and since mark reason:

(78) John went home because he was cold.
(79) Mary sold her books because she failed syntax.
(80) Since it was raining we decided to delay the picnic.
(81) Since Bill once got sick on rattlesnake eggs, he has not been able to eat them.

Now, let us look at the wormhole scenario. In the simplest case, the worm moves through the wormhole without end. There is no cause and effect. That it moves seems to be the case without cause and effect. It is not evident to the casual observer that the worm may be programmed to do so. It is like the universe: it is because it is.

Next let us look at the second scenario. The worm bumps into the end. A message is sent to its IPU. Then the worm send out the message Reverse Movement. There is a cause and effect relation ship here. The first message is the cause of the second message--the effect.


The last theta role known to us is purpose. Purpose is the goal associated with an activity or accomplishment:

(82) Mary went to the story for some milk.

(83) John sold his car in order to save the atmosphere.

(84) Popeye eats spinach so that he will become stronger.

In the wormhole scenario, there is no purpose. The programmed to move, but no purpose has been indicated. Now, if it were the case that the worm got a morsel of nourishment (food) each time he hit the sensor, and if he didn't he would die, then his purpose would be to obtain food to remain alive.

(85)  The worm moves through the wormhole to get food.


The benefactor is the one who benfits from a particular activity or accomplishment.

The wormhole revisited.

Theta roles play an important role in NP raising and Case theory (topics for L322). The above is a sketch of theta roles. Theta roles are closely tied to the meaning of the predicate that assigns the theta role of each argument.

Contents: Experiencer | Locative | Theme | Agent | Wormhole | Experiencer versus agent | Instrument | Possessor | Patient | Constructum | Destructum | Trigger | Location | Goal, Source, and Path | Reason | Purpose | Benefactor | Wormhole Revisited

Go to Theta Roles Continued

Go to raising.

Go to case.theory

Go to tense.aspect.

To return to 322 course outline Click here.

To return to 222 course outline Click here.

This page last updated 25 MR 2002