Ins and outs of the meaning of `is'

THE FATE of the 42nd President of the United States may have depended on his theories of language. In his testimony Clinton expounded on the semantics of the present tense and of the words "alone", "cause" and, notoriously, "sex". Clinton realises that language does have a systematic though complex relation to reality. His semantic arguments, if ultimately unsuccessful, show an acute understanding of the logic and psychology of language.

The world is analog; language is digital. A tape measure shows that people's heights vary continuously, but, when we talk about them, we face a multiple choice between "tall" and "short". We cannot make a sound halfway between "warm" and "cold" to refer to something tepid, and people who describe themselves as "middle-aged" and "wise" cannot pinpoint the instant they became so. Words are anchored to endpoints, but the continuum between them may be up for grabs.

Clinton suggested he was not "alone" with Lewinsky because people were in the Oval Office complex at the time. An intriguing point: since none of us is marooned on an asteroid but shares the planet with five billion others, none of us is ever unambiguously alone. Exactly how far away, how inaudible or invisible or unnoticed before we are willing to say that someone is "alone"? At what point in the continuum of bodily contact do we say that "sex" has occurred? How many times, how closely spaced, before it is "sexual relations" or a "sexual relationship"? When consenting adults come together, does one of them "cause" contact, or are the actions of entities with free will never truly caused?

The argument doesn't impress anyone but a professor of semantics, and that is because of another key feature of language: people work around its limitations by tacitly agreeing on how to use it. Conversation requires co-operation. A speaker implicitly guarantees that the information he is conveying is relevant: that the listener can easily connect it to his prior knowledge and expectations. That allows listeners to hear between the lines in order to pin down vague words, winnow out the unintended readings of an ambiguous sentence, piece together fractured utterances, glide over slips of the tongue, and fill in the countless unsaid logical steps in a complete train of thought. When the shampoo bottle says "Lather, rinse, repeat", we don't spend the rest of our lives in the shower; we infer that it means "repeat once". When Marsha says "I'm leaving" and John asks "Who is he?", we instantly deduce which "he" John is referring to.

The expression "to be on speaking terms" reminds us that, without co- operation, language is impossible. The reason we cannot converse with our computers is not that the engineers cannot program in the grammar and vocabulary of the English language but that they cannot program in the common sense of a human speaker. In the old Get Smart television series, Maxwell Smart asks the robot Hymie to "give me a hand", and Hymie proceeds to unscrew his hand and hold it out.

The sketchiness of language gives the listener considerable leeway in pinning an interpretation to an utterance. That is fine when the interlocutors are co-operative but not when they are adversaries and the interpretation can send someone to gaol. The law requires language to be do something for which it is badly designed: to leave nothing to the imagination. Lawmakers and lawyers do their best to co-opt language for this unnatural job. But at some point we have to fall back on the principle of co-operation and judge the truthfulness of a statement by what a co- operative speaker would expect his listeners to infer.

Clinton astutely said, "My goal in this deposition was to be truthful, but not particularly helpful." Unfortunately, it is in the very nature of human language that this goal is impossible.

Steven Pinker is the author of `How the Mind Works' (Penguin, pounds 9.99)