I have what I hope is not a terribly naive or obtuse question. In discussions of justice in contractual relations, one frequently sees commentators and less occasionally courts refer to exploitation or the idea that a particular contract is exploitive.  Can anyone point toward theoretical literature that tries to rigorously set out the idea of exploitation?  What does it mean for a contract to be exploitive and why exactly is that wrong?

I am not talking about theories of unconscionability so much as the specific idea of exploitation.  It seems like a ubiquitous building block in a lot of normative arguments about contract law, but when I think about it it always seems to be a Potter-Stewart-on-obscenity ("I know it when I see it") kind of concept.

I am hoping that I am just revealing my bibliographic ignorance here, and someone can point me toward some rigorous treatments of the idea.

Best wishes,

Nate