What defines the boundary of one person's freedom? The answer begins with a fact as universal as it is elemental: pain. It is through pain, transmitted by the nervous system, felt in the body, that violations of our freedom and bodily integrity become perceptible. Without pain, we could not recognize aggression. This physiological reality establishes a natural limit to everyone's liberty: any action that causes pain to another constitutes an infringement of their self-ownership.

Gustave de Molinari (1819–1912), one of the most profound thinkers in the French liberal tradition, his career spanned nearly a century, from the age of Louis-Philippe to the eve of the First World War, developed a second dimension of this analysis in his Morale économique. Beyond pain, there is fear: the anticipation of harm, and the inhibition of action it produces. When others infringe upon our rights or pose a credible threat, we are compelled to reconsider and adjust our plans. We cannot act as we would have acted in the absence of the threat. Our effective freedom is diminished, even before any physical aggression occurs.

However, and this is a crucial distinction, not all nuisances are of the same order. Imagine a baker in a small town; a competitor opens a shop across the street. The first baker suffers a real economic nuisance. But is this an aggression that the law should punish? Clearly not. The competitor has not violated anyone's person or property; he has merely exercised his own freedom.

Historical developments reveal a gradual expansion of the nuisances that societies no longer consider punishable. In the Middle Ages, competition itself was often condemned: an inventor's new technique threatened the livelihood of established craftsmen in small, closed markets where the effects were felt acutely and there were few alternative outlets. The progressive emancipation from such restrictions, the recognition that competition and innovation, though they cause discomfort, are not crimes, has accompanied the development of freer and more prosperous societies.

Frédéric Bastiat and Gustave de Molinari often summarized their liberal doctrine in two words: "liberty and peace", or, as they sometimes formulated it, "liberty within, peace without." These are not separate aspirations; they are the natural consequences of the same principles.

The harmony of a free society is rooted in the simplest of economic relationships: that between customer and supplier. The customer needs his supplier to obtain the desired goods; the supplier needs his customer to be prosperous, for a rational merchant prefers wealthy customers capable of acquiring his products to impoverished ones who cannot buy anything. This logic applies at every level: within a family, within a city, between nations. It creates mutually beneficial relationships that naturally engender cooperation and peace.

The Abbé de Saint-Pierre, the great pacifist of the early 18th century, much studied later by Molinari, identified a further fact underpinning this harmony: the universal need for security. No individual, however strong, is strong enough to protect himself alone. The strongest man alive was not strong in childhood, will not be strong in old age, and is not strong at every moment, he sleeps, he falls ill, he weakens. This fundamental vulnerability creates a universal need for collective security, which can only be satisfied through the rule of law: agreed-upon rules that protect each person's liberty and property, enabling peaceful exchange.

Finally, the very evolution of production tends toward peace. Hunting and fishing are, in a sense, violent modes of production, destruction rather than creation. The wheat field represents an advance toward peaceful production: it creates utility where none existed before, without destroying other living things. Modern production, increasingly, embodies the logic of harmony rather than predation, and this tendency has only to be recognized and supported by law to produce truly liberal societies.

Political freedom, though it is a means rather than an end, rests on its own factual foundations. The first is the principle of decentralization, which follows directly from human variety. Human beings are not clones; they have different needs, preferences, and circumstances. This diversity is, above all, individual, not merely regional or national. Logically, decentralization should be pushed to its furthest consequence: individual autonomy.

Benjamin Constant, whom we have already met as a defender of freedom of thought, was one of the most passionate advocates of decentralization. His argument is simple: one cannot plan, organize, or direct a society from a center while ignoring the irreducible diversity of its members. The impossibility of central planning, which we encountered earlier in the limits of human reason, reappears here in the political sphere.

Universal suffrage finds its justification in the same facts. Pleasures and pains are individual: I feel the effects of a law in myself, directly and personally. Others feel different effects and form different judgments. Each person's perception must therefore count, because each contributes information that no central authority could possess. The just law is one that aggregates these individual judgments, not one that is imposed by a minority who presume to know better.

We have already established the factual foundations of freedom of expression and religious tolerance: they arise from the individuality of human personality and the diversity of judgments that follows from self-ownership. Because personalities differ, judgments will, and must, differ as well. This diversity is not an obstacle to truth but the very engine of human perfectibility: it is through the confrontation of different judgments that the best ideas emerge and civilization advances.

Consider one further example: the choice of a spouse. There are, as the saying goes, a thousand shades of beauty and a thousand ways of being happy. Aesthetic and emotional perceptions are profoundly individual, rooted in the unique physiological constitution and life experience of each person. The freedom to choose whom to love and whom to marry is not a luxury; it is a direct consequence of the same human facts that ground all the other liberties.

With this, we have completed our survey of the principal facts that ground the doctrine of liberty. Liberalism, we may now say, is anchored in the facts of human existence, in the body, the senses, the will, the diversity of individuals, the need for security, the logic of exchange. The systems of unfreedom, by contrast, must deny or ignore these facts. It is to their factual contradictions that we turn in the next chapter.