Claiming self-defense requires more than pointing to the mere existence of risk. In everyday moral and legal reasoning, many situations involve uncertainty and a nonzero chance of serious harm, yet they are not treated as grounds for killing another person. The presence of risk alone is not enough; the threat must be sufficiently grave, imminent, and unavoidable to justify lethal force.
Consider a thought experiment: being confined in a small spaceship with someone who unknowingly has an asymptomatic case of COVID-19. The situation could reasonably feel threatening. COVID carries unpredictable symptoms, potential long-term effects, and a measurable risk of death. Even so, it would not be considered reasonable or permissible to throw that person out of the spaceship to protect oneself, because doing so would directly kill them. A roughly two-percent chance of dying is not typically viewed as enough to justify killing another person under a self-defense claim.
This standard matters because pregnancy-related risk is often cited as justification for abortion on self-defense grounds. Yet when the cited risk is even smaller—such as a 0.017 percent risk of death—the justification becomes weaker, not stronger. If killing were permitted whenever someone perceived a risk at that level, the concept of self-defense would expand so broadly that it could be used to justify killing almost anyone who poses even a remote danger.
Self-defense loses its meaning if it no longer distinguishes between grave, imminent threats and ordinary conditions of risk that accompany human interaction. Allowing lethal force based on minimal statistical risk would dissolve the moral limits that make self-defense a coherent and restrained principle rather than a universal permission to kill.
Key Takeaways
Risk alone does not justify killing: Many situations involve real but limited risk, yet society does not permit killing another person as a preventive measure.
Self-defense requires proportionality: A very small risk to one person’s life does not proportionally justify certain death for another.
Lower risk weakens the claim: If a 2% risk cannot justify killing, a 0.017% risk makes the self-defense argument even less credible.
Overexpansion empties the concept: Treating minimal risk as grounds for lethal self-defense would make the principle meaningless and dangerously broad.