Information Structure: Topic and Focus

Speakers do not simply transmit propositions; they package them for the moment. Following Krifka (2007), information structure can be described as a phenomenon of information packaging that responds to the immediate communicative needs of interlocutors. In other words, it concerns how content is arranged according to what the speaker takes the addressee to know or not know. This is closely connected to presupposition: some assumptions are expected to be accommodated and others are not, and that shapes how a message is built.

Two central notions are topic and focus. Drawing on Lambrecht, the topic of a sentence is the thing that the proposition expressed by the sentence is about. Focus, following Krifka, indicates the presence of alternatives that are relevant for the interpretation of the expression. Focus is fundamentally about alternatives; topic is fundamentally about what the sentence is about. The difficulty with topic lies in pinning down what "about" really means.

Focus and the negation of alternatives

Focus is easiest to see through stress. Take My daughter wants pizza. Stressing different elements evokes different alternatives, each of which is then negated. My daughter wants pizza suggests it is mine and not yours; My daughter wants pizza suggests my daughter and not my son; My daughter wants pizza suggests she wants it rather than merely needs it; My daughter wants pizza suggests pizza and not some other food. Without stress there is no such inference: the neutral sentence does not imply she wants nothing else. Focusing an element, then, is the negation of alternatives, marking that it is that element and not the similar options that could fill the same slot. Languages mark focus in different ways, including by moving an element to the front, as in Pizza my daughter wants, but the underlying semantic analysis remains the negation of alternatives.

Topic and the problem of the subject

Topic is harder, because as often defined it sits very close to the grammatical subject. Krifka contrasts Aristotle Onassis married Jacqueline Kennedy with Jacqueline Kennedy married Aristotle Onassis. Since marry is reciprocal, both participants do the same thing, yet the first sentence is about Aristotle and the second about Jacqueline. Whatever sits in subject position is interpreted as the topic. This creates a real analytical problem: if the pragmatic meaning of topic is nearly identical to subjecthood, then a fronted element might be initial because it is a topic or simply because it is the subject, and the two are hard to tell apart. Whether languages posit a distinct syntactic position for topics, and how to separate topic from subject, remains open, and it bears directly on debates over word order in Hebrew and Greek.

Frame setting

A third notion, often lumped together with topic, must be kept distinct. Frame setting, in Krifka's terms, is used to limit the applicability of the main predication to a certain restricted domain. An English example is In terms of what my daughter wants, she wants pizza, where the initial clause delimits the domain under discussion. It is frequently marked by intonation and a pause in English, and by fronting an element in biblical Hebrew. If one chooses to call this "topic" as well, the definition must be made explicit so that frame setting is not conflated with topic proper.