We’ve spent a lot of time thinking about the structure of sentences. We’re now turning our attention to what sentences mean. Sentences usually describe events or states in the world. And events usually have participants: the people or things that play a role in the event. Usually, noun phrases are used to refer to the participants in an event. It turns out that, even across events that are quite different from each other, some participants share some elements of meaning.
Take a look at the underlined phrases in each of these sentences.
Mina tore the wrapping paper.
Sam ran a marathon.
The students studied for their exam.
Neeraja waited for the bus.
Carlos ate the rice.
We can see that the grammatical role of each of these is a subject: They’re all in the specifier of TP. Semantically, the events that each sentence describes are quite different: tearing is different from running which is different from studying or waiting or eating. But even across these different events, the participants described by the underlined noun phrases all share some semantic similarities: all of them choose to take part in the event, all of them are causing the event to happen. Let’s look at another few sentences.
Mina tore the wrapping paper.
A nail tore her skirt.
The fabric tore.
All of these sentences have the same verb and they all describe a tearing event. And all the underlined phrases have the grammatical role of subject, but they don’t share the same semantic properties. In the first sentence, Mina is the one who causes the tearing event to happen: you can imagine her gleefully tearing the paper open to see what’s inside. In the second sentence, the nail is sort of responsible for the tearing, but it certainly doesn’t choose to make it happen. And in the third sentence, the fabric is the thing that the tearing happens to, not the participant that makes the tearing happen. So even though all three of these NPs are subjects, they don’t all share semantic properties.
Remember that we use grammatical roles to label the syntactic position of a noun phrase in a sentence. We’re now going to introduce a new kind of label, called thematic roles. We can use thematic roles to identify common semantic properties of the participants in events. An important thing to notice about thematic roles is that they are independent of grammatical roles. In this pair of sentences,
Kavitha cooked this lovely meal.
This lovely meal was cooked by Kavitha.
the grammatical role for Kavitha is different: Kavitha is the subject of one sentence but an oblique in the other. But semantically, Kavitha’s role in the cooking event is the same in both sentences. We say that Kavitha’s thematic role is the agent.
The kinds of participants that we label as agents tend to have three properties: usually, they are volitional, meaning they choose to participate in the event. They’re sentient, that is, they’re aware of the event, and often they’re the ones that bring the event about or cause it to take place. Let’s look back at that tearing event.
Mina tore the paper.
The paper tore.
Again in these sentences, the paper has two different grammatical roles: it’s the direct object in the first sentence but the subject of the second, but semantically its role as a participant in the tearing event is the same in both: it’s the thing that the tearing happens to. Its thematic role is called a theme, or in some books, you’ll see it called a patient. Theme participants typically undergo events, that is, events happen to them. They’re affected by events, and often they change state or position as a result of an event.
Take a minute and try to think of some sentences that describe events that have agent and theme participants. They’re probably the two most common thematic role labels, and in fact, one theory of semantics says that every participant is either an Agent or a Theme, just to a greater or lesser degree. But it can also be useful to have labels for some other kinds of participants, and the grammars of many languages encode other semantic properties besides those two.
Some languages make a morphological distinction between an animate agent and an inanimate cause. In a sentence like, The hurricane destroyed the houses, the hurricane is clearly responsible for the destroying event, but it’s not sentient or volitional — the hurricane isn’t choosing to bring about the destroying. Likewise, in The movie frightened the children, the movie isn’t really a typical agent. We label these inanimate participants with the label cause. A cause participant shares the agentive property of causing an event to happen, but it’s not aware of the event and doesn’t choose to cause it, because the cause is inanimate.
In this sentence, The knife cut the bread, would you say that the knife is a cause participant? Certainly, the knife is inanimate, and it’s not aware of the cutting event, but it’s also not really causing the cutting to happen, is it? There’s some unnamed agent who must be using the knife to cut the bread. We could label the knife as an instrument. An instrument is the participant that an agent uses to make an event happen.
Many languages have special morphology to indicate the location of an event, like in these sentences:
The Habs won the game at the Forum.
The kids ran through the sprinkler on the lawn.
The parade travelled around the neighbourhood.
The noun phrases the forum, the lawn and the neighbourhood all have the thematic role of location.
So we’ve got labels like cause, instrument, and location to describe some of the roles that inanimate participants typically have in events. I want to return to animate participants to look at one more important role. Let’s look at the human participants in these sentences:
Phoebe tripped on the curb.
Sun-Jin won the lottery.
The movie frightened Farah.
If Phoebe tripped on the curb, it doesn’t seem quite right to label Phoebe as an agent — presumably, she didn’t choose to trip on the curb, even if she is aware of it, and she isn’t really the cause of the tripping event; the curb is. And no matter how badly you might want to win the lottery, you can’t really cause it to happen, so Sun-Jin isn’t a great example of an agent either. Likewise, if we say that the movie frightened Farah, Farah isn’t exactly a theme; yes, the frightening is happening to her, but she’s not necessarily changed by it, and she is aware of the event.
Let’s label these participants with the thematic role of the experiencer. Experiencers are like the middle ground between agents and themes. They are animate and sentient, so they’re aware of events happening, but they don’t necessarily choose or cause events to happen; events happen to them. Because experiencers have this in-between status, they can show up either as subjects or as objects, like in these examples:
The children were scared of the clowns.
The clowns frightened the children.
And we could say that Phoebe and Sun-Jin are experiencers of their tripping and winning events: they don’t cause the events to happen, but they are aware of the events happening.
To sum up, thematic role labels capture the semantic properties of participants in events, independent of the syntactic position of the noun phrase. Just because something has the grammatical role of a subject doesn’t mean it will necessarily have the thematic role of agent and vice versa. There’s a fair amount of argument in the literature about exactly how many thematic role labels are necessary to capture the relevant patterns of behaviour in the languages of the world, with proposals ranging from two to about fifteen thematic roles. We’ll settle on the middle ground and use six thematic role labels: