Ambiguity can be a freeing, positive force in negotiations. It can help those who imagine themselves deadlocked cross a difficult hurdle, even if in a kind of stumble, so the next issue can be resolved.
When enough issues are resolved, conflict becomes an agreement. Progress is made.
Ambiguity can also be a negative influence, allowing some people to pursue the impossible.
In those circumstances, ambiguity becomes a stumbling block. Progress is stymied.
Ambiguity has played an important part in pandemic communications.
In an ever-changing situation, where even vaccine delivery is uncertain, it is unwise to offer certainties — but not always.
Tánaiste Leo Varadkar recognised that when he warned that anyone who declines an AstraZeneca vaccine will have to wait until the entire population is vaccinated before they might be offered an alternative.
Mr Varadkar said:
They would have to wait until the end... it wouldn’t be June or July, it would be later than that.
There is a welcome clarity about that take-it-or-leave-it advice.
Especially as it means that anti-vaccination campaigners must decide whether to stand by their anti-science beliefs or protect themselves from the pandemic.
Mr Varadkar is right to remove dangerous ambiguity from this conversation.
After all, a vaccination programme is no more than medicine, providing society with a safety net, and a falling man can hardly choose one safety net over the other.