and emotional suffering of those who are caught in it, and of the motivations of those who practice it. In other words, slavery is a dense descriptor, an idea that is easily referenced and that brings with it a slew of properties, feelings, norms, and expectations. The use of a dense descriptor in a metaphor prompts a listener to unpack those aspects of the descriptor that seem relevant to the target/tenor. This conciseness comes at a price, as the listener may associate different feelings and properties with a concept like slavery, or may unpack the descriptor to focus on different aspects than those of interest to the speaker. For instance, a speaker may employ the concept of slavery to focus on the domestic abuse, emotional and physical, suffered by one who is trapped in a bad marriage, while the listener may instead unpack the reference to focus on the institutionalized nature of marriage and slavery. Yet the indeterminate nature of metaphor, a natural consequence of its concision, is often a desirable quality of a conceptual pact. One rarely uses metaphor to communicate a rigid set of facts or beliefs. Rather, metaphors introduce a set of talking points for a target, so that speaker and listener might converge toward a mutual understanding, if not of a target idea then of each other’s views of the target. The indeterminacy of metaphor makes it a flexible form of communication. While literal language commits a speaker to a fixed interpretation, and offers little scope for the listener to contribute to the joint construction of meaning, metaphorical language suggests a looser but potentially richer meaning that is amenable to collaborative elaboration by each participant in a conversation.
The densest descriptors are the familiar stereotypes that get used time and again in our metaphors and our similes. Although every concept has the potential to be used figuratively, casual metaphors tend to draw their dense descriptors from the large pool of stereotypes shared by most speakers of a language (see Taylor [1954]). Because so many familiar stereotypes have polarizing qualities—think of the endearing and not-so-endearing qualities of babies, for instance—they serve as ideal vehicles for a metaphor that aims to convey a strong affective stance toward a topic. Even when stereotypes are not used figuratively, as in the assertion “Steve Jobs was a great leader,” they are often likely to elicit metaphors in response, such as “yes, a pioneer,” or “a true artist!” or even “but what a tyrant!” Familiar proper-named entities can also be used as dense descriptors, as when Steve Jobs is compared to the fictional inventor Tony Stark, or Apple is compared to Scientology, or Google to Microsoft. Metaphors are flexible conceits that draw on dense descriptors to concisely suggest a position on a target idea while seeking elaboration or refutation of this position from others. Our computational models for the interpretation of metaphors must thus allow speakers to exploit the same flexibility of expression when interacting with machines as they enjoy with other humans. Such a goal clearly requires a computational system to possess, or acquire, a great deal of knowledge, usefully clustered into dense pockets of properties, feelings, and expectations that can be evoked with a single word or idea.
2.2 THE “MEANING” OF METAPHOR
If metaphor is as much a process as a product, what then is the meaning of any given metaphor? We can point to the linguistic rendering of a metaphor and say that this string is a linguistic metaphor. We can point to the conceptual structure underpinning this linguistic rendering—and to other renderings of the same conceit—and say that this deep structure is a conceptual metaphor. But to what can we point and say: this is the meaning of this metaphor? The problem of metaphor meaning can be approached from a number of perspectives. We can talk of the truth value of a metaphor, much as we can talk of the truth value of any proposition. We can talk of a specific interpretation of a metaphor. Or, we can talk of the specific inferences that a metaphor licenses in the mind of the hearer, as well as the emotions for the target that it is likely to engender in a hearer.
Although most metaphors are literally false, truth value is a remarkably poor guide to the metaphorical nature of any statement. The assertion that “Barack Obama is a Muslim” is no more a metaphor because it is false than “Al Gore is not a robot” is not a metaphor because it is true. For logicians and philosophers, meaning resides not in truth values but in truth conditions, the set of criteria that, if true, would make a statement true as a whole. For instance, in semantic theory in which “Barack Obama” denotes the President of the United States in 2015, and in which “Muslim” denotes the set of all people who profess faith in the religion of Islam, the key truth condition for “Barack Obama is a Muslim” is whether the former individual is a member of the latter set. Different speakers may bring different definitions and denotations to bear on an utterance, and so it is sufficient for some political critics to define the truth condition of “being a Muslim” as membership in the set of people born of at least one Muslim parent, or as membership in the set of people born or raised in predominantly Muslim countries. However one finesses the denotations, “Barack Obama is a Muslim” has different truth conditions than “Barack Obama is a socialist,” as each hinges on membership in different (albeit possibly overlapping) sets, regardless of whether both statements ultimately have the same truth value.
As if defining the literal truth conditions of a predication such as “being a Muslim” or “being a socialist” weren’t hard enough, metaphor poses a further, rather special challenge to the truth-conditional view of meaning. What, for instance, are the truth conditions of the statement “Barack Obama is the Cicero of the 21st Century?” One often needs as much creativity to assign truth conditions to a metaphor as to invent one in the first place. For truth conditions are neither as authoritative or as absolute as they seem, nor are they designed by experts to be shared by all. Rather, truth conditions are often speaker-relative and context-sensitive. One speaker may think that to truthfully call one a socialist, it is enough that this person openly espouse socialist values. Another may think it sufficient for one to act like a socialist, whether one actually thinks of oneself as a socialist or not. These speakers are likely to disagree over the truth conditions of the statement “Barack Obama is a socialist,” yet this is not a problem for metaphor or for language. The truth conditions of a metaphor often arise from a tacit negotiation between speaker and hearer of the meaning of the metaphor, rather than the other way around.
Philosophers who are otherwise bullish about truth conditional semantics are often bearish toward the idea in the context of metaphor. Donald Davidson, for instance, questions the usefulness of truth conditions for arriving at the meaning of a metaphor. For Davidson [1978], a metaphor does not so much communicate a meaning as inspire a meaning, leading him to argue that “the attempt to give literal expression to the content of the metaphor is simply misguided.” Thus, in the metaphor “my car drinks gasoline,” only some of the truth conditions associated with literal uses of the verb to drink will be applicable in the metaphorical context of a drinking car, but none of these carry the weight of the interpretation that the speaker hopes to inspire in the listener (for instance, that my car requires too much gasoline to operate). These truth conditions include, for instance, the expectation that the drinker is an animate creature, that the substance consumed is a potable liquid, and that the drinker both consumes the liquid and derives some chemical benefit from it. Just two of these truth conditions are sensible for the metaphor “my car drinks gasoline,” namely that my car consumes gasoline and derives some chemical value from it. In effect, this is the truth-conditional equivalent of Aristotle’s strategy (b), whereby the species to drink is displaced onto its genus to consume. However, to suggest that this banal observation is the speaker’s intended meaning is to fly in the face of Grice’s maxim of informativeness (see Grice [1978]), since the claim of gasoline consumption holds for most cars and is hardly worth mentioning in the context of this car. Rather, as we can expect most listeners to know that cars consume gasoline, that people generally only drink what they want to drink (and thus drink what they like), then the speaker’s most likely meaning is my car likes to drink gasoline and thus consumes a lot of gasoline, rather more than I would prefer. This meaning cannot be derived from the truth-conditional semantics of the words in the metaphor, but can only emerge from a pragmatic understanding of the world knowledge behind the words.
Black
