In "The Scarlet Letter," what important question related to Hester's crime is still unanswered?

The most important unanswered question in Hester's community is the identity of the baby's father. The adulteress is known (and branded with the scarlet "A"), but who is the adulterer?

However, while this may be the most obvious question that remains, The Scarlet Letter also poses others.  Hawthorne, for instance, opens up the whole nature of sin and sinners--Hester may wear the letter that marks her as a criminal, but Hawthorne shows us that the issue of sin is not so easily defined. Hester, despite her adultery, is ultimately a figure to be admired. In this way, the meaning of the "A" is also unanswered, to some extent.  Throughout the novel, Hawthorne repeatedly shows us the different meanings of Hester's mark, many of which are positive.