Symbiosis — the long-term interaction between different biological species — comes in three forms: mutualism (both benefit), commensalism (one benefits, the other is unaffected), and parasitism (one benefits at the other's expense). Living Value Theory finds in this taxonomy a model for thinking about value exchange more broadly.
Mutualistic exchange is the paradigm case: a transaction in which both parties gain value. But the interesting cases are the others. Commensal exchange — in which one party gains while the other is indifferent — is far more common in social life than we usually acknowledge. And parasitic exchange, in which one party's gain is the other's loss, is the dark underside of every value system.