A Mercy is somewhat of a new departure for Morrison in that she addresses variances in the historicity of slavery, an historical perspective very much overlooked. She describes the lives, feelings, and experiences of servants who were not necessarily captured victims of mercenary slave trade crimes but who may have sold themselves into indentured servitude (as Swift refers to in relation to the Irish people in his ironic political pamphlet "A Modest Proposal"); who may have been purchased and thus vulnerable to resale; who may have been captured after warfare; etc. Morrison also describes the impact of psychological slavery such as the blacksmith--a nameless, therefore perhaps allegorical character--describes to Florens when she becomes emotionally attached to him.
the blacksmith ... never once looked at Florens standing nearby, not breathing ....
Another point for an essay may be that Morrison seems to be exposing a different side of slavery that isn't as dehumanizing as it isn't predicated on racial and ethnic hatred, thus setting up a new paradigm to counter racial hatreds prevalent today. Another point is that she also seems to be using slavery as a metaphor for universal psychological battles of everyday living that enslave and incapacitate freedom. A related idea is that verbal expression, such as Florens' expression through writing, can liberate psychological slavery and replace psychological slavery with personal freedom. This is an idea she introduces at the outset of Florens' narrative:
Stranger things happen all the time everywhere. ... I know you know. One question is who is responsible? Another is can you read? ... Once every seven days we learn to read and write.