The one duty

[ian2]

Oscar Wilde said: "The one duty we owe to history is to rewrite it.”

I think "the one" is frequently used in English. What does it exactly mean? Does "the one duty" mean "special duty", or "the only duty", or "special and only duty"? Could you elaborate on the following three:



1. a duty
2. the duty
3. the one duty


Thanks.

[Anglika]

1. a duty = any responsibility [He has a duty to support his children]
2. the duty = a particular responsibility [The duty of a parent is the support of his or her children]
3. the one duty = the specific/only responsibility [The one duty that all parents have is the support of their children]

Oscar Wilde was intending "only responsibility".