Illness can be modeled either as external invasion or as an inherent system state.

Evidence

Death (termination, entropy) is inexorable. But how should one regard illness and other disturbances of “normal” functioning? One possibility is the familiar “bacterial” explanation, and its extensions: diseases result from the invasion of organisms by virulent micro-organisms, and disabilities result from diseases, or from accidents, or from the consequences of other external matters (like dominant parents or competitive siblings). Diseases and disabilities are thus contingent—pathological. The alternative is to regard them as particular routine states of the living system: stress on systems is always present; the system defends and usually maintains itself through homeostatic devices, sometimes to avoid disturbance altogether, sometimes to recuperate; thus both illness and health essentially are intrinsic matters of the state of biological systems in interaction with their contexts. — John T. Jost and Jim Sidanius, Political Psychology, 4272

Categorization

• DEFINE: Introduces the contingency vs. inherency distinction via a medical frame: pathology-as-invasion versus pathology-as-homeostatic-state.
• XREF: Connects to the contingent-vs-inherent framework the author applies across chapters to political violence and culturalist vs. rational-choice theory.