Fever vs hyperthermia: regulated shift vs lost control

Fever and hyperthermia look alike but are opposite in regulatory status. Fever is a sustained sub-spinodal pyrogen bias that moves the regulated set value UP (to 1.3195 from 1.1832) -- perturb it and it returns to the elevated setpoint. Hyperthermia is a supra-spinodal external heat load that DESTROYS the regulated basin (runaway).

RG3. Same substrate, opposite outcome. Fever = regulation intact at a higher setpoint; hyperthermia = regulation lost. The distinction is whether the drive stays below the spinodal. Mechanism [V]; the setpoint-shift magnitude is [L]; absolute temperature is [O].

Fever: a regulated upward shift

The pyrogen bias is sub-spinodal (True), so the basin survives but its position moves up; a perturbation returns to the elevated setpoint (True). The body is not failing to cool -- it is DEFENDING a deliberately raised target.

Hyperthermia: control destroyed

An external heat load above the spinodal destroys the regulated well (True): there is no setpoint left to return to, and the state runs away. The clinical difference -- treat the cause vs cool immediately -- falls straight out of which side of the spinodal the drive is on.