Galtland Index

The Factual Potential of Harm

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The Factual Potential of Harm

Libertarian legal theory forbids initiated force and permits defensive force, which makes the boundary between them load-bearing — and it is usually drawn with the word proportionality. Os Fundamentos Objetivos da Justiça argues that this is not an answer. Proportionality is the conclusion one wants to reach; it is not a criterion for reaching it, and while it stands in for one, the limit of self-defence depends on the intuition of whoever judges afterwards. The book proposes a measurable quantity in its place.

Why proportionality is not a criterion

The objection is methodological, and it is the same one the book makes against age thresholds for consent: a standard that cannot be applied without importing the judgement it was supposed to supply has not done any work. Saying a defence must be proportionate tells a defender nothing at the moment of decision and tells a tribunal nothing afterwards except to consult its own sense of the matter. For a theory whose entire ambition is to replace arbitrary criteria with demonstrable ones, that is a hole at a critical point.

The measure

The replacement is defined in terms of capacity rather than outcome or intent:

O Potencial Factual de Dano corresponde ao maior nível de lesão que determinada conduta possui capacidade objetiva de produzir sobre a esfera jurídica de outro indivíduo, consideradas todas as circunstâncias concretas conhecidas no momento da defesa.

— Luiz Liberatus and Pedro Távora, Os Fundamentos Objetivos da Justiça

The factual potential of harm is the greatest level of injury a given course of conduct is objectively capable of producing on another’s juridical sphere, given all the concrete circumstances known at the moment of defence. What enters the assessment is the means employed, the aggressor’s objective capacity, the victim’s vulnerability, physical or numerical superiority, the presence of weapons, the environment, and the information actually available in that instant.

Two features of the definition matter. It is indexed to the moment of defence, not to what turns out afterwards to have been true — a defender is judged on the situation they faced, not on the one reconstructed later. And it is a measure of capacity, not of the aggressor’s subjective intention. Intention enters only when it can be objectively known, and then merely as one more circumstance: the book’s own illustration is that a teacher briefly confiscating a pupil’s phone and a stranger snatching the same phone on the street are near-identical physical acts with entirely different factual potentials, because the surrounding facts differ.

The scale

Within each category of right threatened — property, physical integrity, life — the book grades aggression into four levels by objective capacity to injure:

  • Level I — violation without relevant injury. Conduct that breaches the sphere without significant capacity to cause physical harm: throwing water, spitting, unauthorised touching, deliberately breaking the legitimate protective space.
  • Level II — minor injury. Conduct capable of producing pain or small injuries: light shoves, slaps, pulls, immobilisation.
  • Level III — significant injury. Conduct capable of fractures, cuts, trauma or serious incapacitation: heavy punches, kicks, blows with blunt objects.
  • Level IV — lethal potential. Conduct objectively capable of causing death: gunshots, knife strikes to vital regions, strangulation, objectively lethal group assaults.

The grading attaches to circumstances rather than to gestures. The same shove has a completely different potential from a child, from a trained adult, and at the edge of a precipice.

The book also recognises a legitimate protective space — a physical distance one may maintain to prevent bodily invasion. It is not a separate property but a functional extension of protecting one’s physical integrity, and the book’s claim about breaking through it is deliberately hedged: doing so may represent an intensification of the threat, not that it always does. This is what lets defence begin before contact, which the book argues it must: requiring the aggression to be completed first would mean rights can only be protected after they have been violated.

Who bears the uncertainty

The most consequential rule in the chapter handles the ordinary case where the victim cannot actually measure the danger — the night-time home invasion, the approach of someone apparently armed, any situation offering no time to assess:

Quem cria objetivamente uma situação de incerteza sobre o Potencial Factual de Dano assume as consequências jurídicas dessa própria incerteza.

— Luiz Liberatus and Pedro Távora, Os Fundamentos Objetivos da Justiça

Whoever objectively creates a situation of uncertainty about the factual potential of harm assumes the legal consequences of that uncertainty. It is not for the victim to gamble their own juridical sphere to discover whether the threat was smaller than it appeared; the risk belongs to the aggressor who voluntarily produced it.

This is paired with a burden-of-proof rule pointing the same way. Defensive excess is never presumed: whoever alleges that a defence exceeded the factual potential of harm must demonstrate it objectively, and absent sufficient proof the defensive action is presumed legitimate — because the aggressor is the one who originated the conflict. Together these place both the epistemic and the evidential cost of a violent situation on the person who created it.

The limit remains real. Defence stays legitimate while its intensity is necessary to stop the aggression and consistent with the potential the threat objectively presented; past that point it stops preserving a sphere and becomes a fresh aggression of its own. And it ends when the threat does — force continued after the need has gone is assessed like any other intervention.

The twin test for externalities

The same method is applied to a problem the non-aggression principle handles badly: pollution, noise and nuisance, where the harm is a by-product of legitimate activity on one’s own property. The book’s premise is that if every external effect counted as aggression, property could not be used at all — talking produces sound, cooking produces odours, and a factory alters everything around it.

Its measure is the Factual Impact of the Externality: the degree of objective alteration an activity produces on others’ juridical spheres, assessed through intensity, duration, frequency, predictability, extent of area affected, nature of the activity, the condition existing beforehand, and which right is touched. As the book’s own summary has it, direct aggression is analysed by the factual potential of harm and externalities by the factual impact — the same move each time, replacing a vague notion with a graded objective one.

Effects are then sorted by the right affected: no relevant legal harm (seeing a neighbour’s construction, hearing ordinary sounds); reduced use of property (excessive noise, invasive lighting, persistent vibration); patrimonial damage (contaminated water, pollution degrading buildings or crops); and harm to physical integrity or life. The decisive question is never annoyance but whether an objective alteration of another’s sphere occurred.

A priority principle completes it: an externality already objectively present in an environment forms part of that reality, so someone who buys a house next to a church that rings its bells acquires it with the bells. But priority is not a licence to expand — an existing activity has no right to increase its externality indefinitely, and a significant change in its character is assessed afresh. This is close to the coming-to-the-nuisance reasoning familiar from Rothbardian treatments of pollution, derived here from the delimitation of spheres rather than from homesteaded easements.

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Galtland Index. “The Factual Potential of Harm.” https://index.galtland.org/concepts/factual-potential-of-harm

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