I need help here.
Is there a term for or a historian who reads primary sources and draws interpretations based on the information that is not there.
Like reading the gaps in sources of eg, rich white man and trying to piece together the story of his black slave.
To study the gaps and to come out with conclusions.
Do you mean speculation?
As in: "the historian is unsure why the rich man has disappeared in his sources from 1750 to 1751 but he speculates that he went to the western front."