When most people think about the immune system, they think about defense. Germs invade, the immune system recognizes the danger, and specialized cells attack and destroy the intruders. We are accustomed to describing this process in military language: invading armies, defensive barriers, killer cells, surveillance, mobilization, and victory or defeat. It is an understandable description, but it is incomplete. The immune system does much more than fight enemies, and understanding its other functions may help us think differently about the health of human societies.
For more than a century, scientists have been asking what the immune system actually does. One of the most interesting contributions to this question comes from physician and philosopher Alfred I. Tauber, whose 2017 book Immunity: The Evolution of an Idea traces the changing scientific understanding of immunity. Tauber challenges the assumption that immunity is primarily a matter of distinguishing what belongs to the body from what does not. Instead, he presents the immune system as a dynamic network of processes through which living organisms maintain their integrity while continually interacting with an ever-changing environment.
This is a profound shift in perspective. It suggests that the purpose of immunity is not simply to defeat what is foreign, but to sustain the conditions that make continued life possible.
The Problem with Self and Other
For much of the twentieth century, immunology was organized around the distinction between self and nonself. The immune system was understood as recognizing the body's own tissues and protecting them against foreign organisms or substances. This model proved enormously productive, helping scientists explain important features of infection, transplantation, and immune recognition.
But the body presents a more complicated reality. Human beings are inhabited by enormous communities of microorganisms, many of which contribute to digestion, metabolism, and other essential functions. We depend on substances from outside ourselves for nourishment, and our immune systems must continually distinguish harmless encounters from potentially dangerous ones. Meanwhile, immune cells participate in clearing away dying cells, responding to tissue damage, and maintaining physiological balance.
Foreignness alone cannot determine what is dangerous. Something originating outside the body may be essential to its well-being, while something arising within the body may become destructive. Cancer, for example, develops from the body's own cells. Autoimmune diseases occur when immune responses damage the tissues they would ordinarily help protect.
The immune system must therefore do something considerably more sophisticated than divide the world into friends and enemies. It must respond appropriately to different conditions, sometimes attacking, sometimes tolerating, sometimes repairing, and sometimes restraining its own activity.
Identity Is Something Living Systems Maintain
Tauber's historical analysis returns to Élie Metchnikoff, one of the founders of immunology, whose late nineteenth-century work introduced a broader understanding of immune activity. Metchnikoff was interested not only in how organisms defend themselves against infection, but in how diverse and potentially competing cellular populations become integrated into a functioning living whole.
This question remains fundamental to biology. Multicellular organisms are composed of differentiated cells that perform specialized functions. Those cells must coordinate their activities, exchange information, respond to changing conditions, and constrain behaviors that threaten the larger organism. The organism's continued existence depends upon the maintenance of relationships among its constituent parts.
The immune system participates in this ongoing work. It helps maintain the conditions under which different elements can continue functioning together. Some components must be eliminated, others repaired, and still others accommodated.
From this perspective, biological identity is not simply a fixed possession established at birth. It is also a continuing accomplishment, sustained through development, adaptation, and relationships with the surrounding world.
That insight has implications far beyond immunology, although we must be careful when moving from biological explanation to social analogy.
What This Means for Human Societies
Human societies are not biological organisms in the literal sense. People are conscious individuals with moral standing, rights, histories, relationships, and the capacity to make choices. No society possesses a biological immune system equivalent to the one operating inside a human body.
Nevertheless, societies face some remarkably similar organizational problems. They must maintain enough coherence to survive while allowing the differences, exchanges, and adaptations upon which their continued existence depends. They must protect against genuine threats without confusing every unfamiliar person, idea, or activity with danger. They must repair damage, preserve memory, coordinate specialized functions, and respond to changing circumstances.
These requirements provide the foundation for the concept of a social immune system: the distributed capacities through which people, communities, and institutions recognize threats, restrain destructive power, preserve trustworthy information, protect vulnerable members, and repair the conditions necessary for collective life.
The analogy becomes especially useful when we move beyond the idea of defense alone.
Consider a healthy democratic society. Its continuing vitality depends upon differences in experience, knowledge, occupation, culture, and perspective. Scientists, educators, journalists, caregivers, public servants, artists, and countless others perform specialized functions that contribute to the larger social whole. They will not always agree, nor should they. Differences can generate discovery, creativity, criticism, and correction.
A healthy society must distinguish among differences that enrich collective life, conflicts that require negotiation, and behaviors that genuinely threaten the rights, safety, and continued functioning of others.
When that capacity deteriorates, societies become vulnerable in two directions. They may fail to recognize genuinely predatory behavior, allowing powerful individuals or institutions to exploit others and undermine protective arrangements. Or they may begin interpreting ordinary differences, criticism, and dissent as existential threats, mobilizing their protective capacities against the very people whose participation sustains collective life.
These failures may reinforce one another. A leader or institution that portrays critics as dangerous enemies may weaken the independent sources of information and accountability that would otherwise help society recognize genuine abuses of power.
The problem, therefore, is not simply inadequate defense. It is impaired discrimination: a growing inability to recognize the difference between danger and difference.
When Protection Becomes Destructive
The biological immune system offers another important lesson. An immune response can cause damage even when it is activated in the name of protection. Excessive inflammation may injure healthy tissues, and autoimmune diseases demonstrate that immune activity can become destructive when regulation fails.
We should not confuse these biological conditions with political or psychological diagnoses. Social groups do not literally develop autoimmune diseases. But the analogy allows us to ask an important question: What happens when institutions created to protect collective life begin damaging the relationships, freedoms, and public capacities that make that life possible?
A government may justify repression as necessary for public safety. An organization may silence criticism in order to preserve its reputation. A community may exclude vulnerable members because they have been portrayed as threats. In each case, protection can become the justification for actions that diminish the integrity of the larger system.
This is why social immunity must include the regulation of power itself. A healthy society needs not only mechanisms for responding to external threats, but protections against the misuse of its own authority.
Independent courts, a free press, scientific inquiry, public accountability, education, civil rights, and the ability to challenge those in power serve different functions, but together they help societies identify errors, expose abuse, and correct destructive developments before they become irreversible.
Their value rests partly in their independence. When all the institutions responsible for detecting and correcting danger become subordinated to a single center of power, the larger society loses essential capacities for self-correction.
The Positive Work of Social Immunity
There is another side to this argument that deserves equal attention. A healthy immune system does not spend every moment fighting infection. Much of its work is quiet, continuous, and largely invisible. Its contribution to ordinary physiological functioning does not attract attention in the way an acute illness does.
The same is true of healthy societies. Much of the work that preserves collective life occurs through ordinary activities: teaching children, caring for people who are ill, preserving accurate records, maintaining public infrastructure, resolving disagreements, transmitting knowledge, preventing violence, and helping those who have been injured recover.
These are not secondary activities to be supported only after the supposedly more important business of defense has been completed. They are among the conditions that make a society worth defending.
This is where the biological analogy connects with the broader concept of biocracy: the idea that human institutions should be organized to sustain the conditions necessary for living systems to flourish, rather than allowing concentrated power to consume the resources and relationships upon which collective well-being depends.
The health of a society cannot be measured solely by its ability to defeat opponents. We must also ask whether it can sustain cooperation, tolerate differences, care for vulnerability, preserve knowledge, resolve conflicts without unnecessary violence, and repair the injuries that inevitably occur in collective life.
These capacities require continuing attention. They cannot be established once and then presumed to endure indefinitely. Like biological organisms, societies change over time, and the relationships sustaining their integrity require renewal.
From Defense to Wisdom
The expanded understanding of immunity described by Tauber provides an important starting point, but human societies confront questions that biology alone cannot answer. An immune system does not formulate a conception of justice, deliberate about human rights, or decide what obligations one generation owes another.
Human beings can do these things, although our capacity to act wisely remains unevenly developed.
Wisdom requires more than intelligence and more than the ability to recognize danger. It requires integrating knowledge with memory, emotional understanding, concern for others, ethical responsibility, and an appreciation of the long-term consequences of our actions.
A society may possess extraordinary technological and military power while remaining dangerously immature in its use of that power. It may gather immense quantities of information while losing the ability to distinguish truth from manipulation. It may develop increasingly powerful mechanisms of protection without developing the wisdom necessary to prevent those mechanisms from being turned against its own people.
The lesson we can draw from the changing science of immunity is not that biology provides a ready-made blueprint for democratic government. It is that continued life depends upon more than resistance to enemies. It depends upon the maintenance of complex relationships, the regulation of destructive processes, the accommodation of beneficial differences, and the capacity to adapt without destroying the whole.
For human societies, we must add something further: the moral responsibility to protect the people whose lives constitute that whole, including those who are vulnerable, unpopular, unfamiliar, or unable to defend themselves.
The ultimate purpose of a healthy social immune system is not to create a society without differences, conflict, or vulnerability. It is to sustain a society capable of living with those realities without surrendering to predatory power or destroying itself in the name of protection.
Scientific foundations and further reading
Tauber, A. I. (2017). Immunity: The Evolution of an Idea. Oxford University Press. Particularly the Introduction and Chapter 1, “A History of the Immune Self.”
Buss, L. W. (1987). The Evolution of Individuality. Princeton University Press.
Gilbert, S. F., Sapp, J., & Tauber, A. I. (2012). “A Symbiotic View of Life: We Have Never Been Individuals.” The Quarterly Review of Biology, 87(4), 325–341.
About this series: This essay accompanies The Social Immune System: How Predatory Power Captures Democracy and How We Can Learn to Resist, by Sandra L. Bloom. It draws upon biological research to explore social and institutional health. The social applications are interpretive analogies, not claims that human societies literally possess biological immune systems.