Some people hold this view not by choice, but by biology. In clinical terms it’s associated with psychopathy, or antisocial personality disorder if you prefer more neutral language. These individuals can perform acts that would emotionally devastate most people while experiencing little to no internal response. Importantly, the vast majority of psychopaths are not violent criminals or serial killers.

This isn’t speculative philosophy. Psychopathy is a well-studied area of psychology and neuroscience, and we can identify brain patterns that allow clinicians to assess psychopathy with a high probability of being correct. This gives us something close to a real-world example of the “perfect stoic,” taken to an extreme beyond what any philosophy actually advocates. What’s striking is that psychopathy is strongly associated not with superior functioning, but with impulsivity, poor long-term planning, and difficulty integrating into society.

The takeaway is uncomfortable but important: emotions are not merely noise that interferes with rationality. They function as behavioral guardrails. Remove them entirely and pure logic alone is insufficient to regulate behavior in a social world. Without those constraints, people don’t become hyper-rational idealists. They become unstable, maladaptive, and conspicuously out of place.

I think the main reason is that social behavior is not rational as a first-order effect. It is irrational at the local level and only becomes rational indirectly, sometimes as a side effect of a side effect.

For example, if I see someone on the street who has just been stabbed, the strictly first-order rational response is to ignore it and keep walking. Helping costs time, energy, and introduces personal risk. From a narrow perspective, conserving resources dominates. Why spend calories calling an ambulance when ignoring it is cheaper?

The second- or third-order effects are where things change. Someone might see you help and treat you differently later, or the person you helped might repay you in some way. But in any single instance, those payoffs are unlikely. Most of the time you get nothing. Likewise, any stigma for not helping can evaporate quickly. People have short memories.

The real effect shows up in aggregate. If you consistently apply this kind of extreme local rationality minute to minute, people notice. Over time, patterns form. You are perceived as cold, unreliable, or unsafe to depend on, and you are gradually shunned. It’s not even the second-order effects that matter most, but the cumulative aggregation of them.

This is where evolution matters. Natural selection is the ultimate trial-based selector. It does not care about what is logically defensible in a single instance. It selects for strategies that survive repeated interaction with reality over long time horizons.

But selection does not operate only at the level of isolated individuals. Humans evolved in groups, and many traits exist specifically to regulate group dynamics. Emotions such as empathy, guilt, shame, and moral outrage function not just to guide personal behavior, but to coordinate groups and enforce norms. They create alignment without requiring explicit calculation.

Just as importantly, groups evolve mechanisms to identify and prune individuals who don’t internalize those constraints. Someone who consistently defects, exploits, or optimizes locally at the expense of others may do fine in isolated interactions, but over time they are marked, excluded, or expelled. This pruning is not moral. It is functional. Groups that fail to do it collapse under free-riding and mistrust.

Seen through this lens, emotions are not optional. They are load-bearing components of social systems. They bias individuals toward cooperation and simultaneously give groups tools to detect and remove those who can’t or won’t play by the same rules.

Natural selection already ran this experiment at scale. Psychopathy illustrates what happens when these mechanisms are weakened or absent. What remains is not a superior form of rationality, but a system that optimizes locally, destabilizes its environment, and ultimately selects itself out.

In that context, stoicism is best understood not as a prescription to remove emotion, but as an attempt to discipline it. Whether it succeeds depends on how narrowly or literally it is interpreted. Taken as emotional suppression or pure rational control, it collapses into the same failure modes already visible in the clinical and evolutionary evidence. Taken more loosely, it functions less as a truth about human behavior and more as a coping framework with limited scope.