Parasitism as Displacement Exchange: Zero-Sum Attractor Competition, Endoparasitism, and Cancer as Intimate Self-Parasitism

Parasitism is formalized as a displacement exchange in which the parasite reduces its own D(xi) at the cost of increasing D(xi) in the host — zero-sum or negative-sum. The parasite spectrum runs from ectoparasite (easy immune recognition) through endoparasite, cellular parasite, genomic parasite, to cancer (clone of self, maximal intimacy, minimal immune recognition). Cancer is the terminal case: a defector clone using the host's own infrastructure, with no evolutionary brake on host destruction.

Mutualism is the opposite: positive-sum displacement exchange where both organisms move toward S0.