Why use implicit communication? Wouldn't life be so much simpler if people just said what they meant? Perhaps, but it would also be much poorer, for it would lack the power of poetry and possibility. Although most self-help books on public speaking and effective communication focus on clarity, everyday language draws extensively on the more covert art of the unsaid: suggestion, insinuation, connotation and other forms of implicit communication. The very abundance of terms with which we differentiate nuances of what hasn't quite been said suggests that this is an area of experience that matters to us.

So why does it matter? One reason is that by not committing to a position or proposition overtly, we can keep our options open for longer. A definition of so-called "diplomatic language" is language that sits on the fence. Equivocation doesn't only provide us with room for manoeuvre, but also allows for plausible deniability: one can't be held accountable for what one hasn't said. Although fudging serves the speaker well, it may frustrate those parties who require decision and commitment.

Another reason for preferring implicit communication has to do with face: because in-your-face remarks tend to cause offence, politeness often involves the use of indirect language. Loss of face can all too readily lead to retaliation and the escalation of conflict. The damage caused by WikiLeaks was not so much in the content of the cables, but in the fact that this content was broadcast: by projecting private communications into the public domain, the judgments they contain are "out there" and can't be taken back (See Steven Pinker's analysis of the film When Harry met Sally in his lecture Language as a Window into Human Nature. In its second sense of "politeness" and "consideration" therefore, diplomatic language serves the interests of the other party by not causing offence, while also serving our own interests by sparing us the consequences of offence caused.

A third and vitally important reason for resorting to implicit communication concerns persuasion: we are much more likely to win someone over if we lead them to the conclusions we want them to reach than if we tell them what to think or do. One way of achieving this is through the use of connotations, which pack a whole story into a capsule. Consider the terms "security fence" and "apartheid wall": both refer to the same edifice between Israel and Palestine, but each tells a very different story.

Metaphors and analogies similarly pack a story in a capsule, as illustrated by the "roadmap" to peace, "war" on terror, or another "Vietnam". Metaphors frame an argument by transferring our understanding of one thing on to a different area of experience. Their appeal is in offering an accessible way of thinking about something we might otherwise find hard to grasp, but they do so by telling only part of the story and leaving the rest to be inferred. In filling out the unsaid along the lines intended by the metaphor-maker, we are in effect complicit in our own manipulation. Diplomacy, it has been said, is "the art of letting the other party have things your way".

Is the use of implicit communication primarily self-serving then? Not all social dynamics are necessarily self-interested, or if they are, the "self" may involve a larger group. This is the case where what is not said need not be said, because it is understood. When we "speak the same language", we understand one another without having to spell out our meaning, as is typified by humour, irony, shared allusions and other forms of coded communication. Here, the unsaid serves to create and consolidate a sense of community.

Finally, the unsaid is packed with the power of possibility. Poetry and politics share common ground when it comes to potential, promise and redress, as suggested by the adage: "We campaign in poetry, but govern in prose." In so far as explicit communication is the tip of the iceberg, implication is its submerged under-structure: unsaid, often unseen, potentially lethal yet at times unutterably beautiful.

From equivocation to consideration, from persuasion to in-group consolidation, from threat to thrall, implicit communication plays an important role not only in diplomacy, but in everyday communication. We have a choice either to master the unsaid or to be mastered by it.

• Biljana Scott will be speaking at Brighton Festival on Sunday 13 May at 4pm in an event called The Unsaid: Diplomatic Incidents