In the tradition of the Catholic Scholastics, the School of Salamanca was a group of intellectuals based in the University of Salamanca in Renaissance Spain who developed what would become the principles of Natural Law and what we consider libertarianism today. They based their philosophy on the works of St. Thomas Aquinas as well as Scripture and laid the foundation for a more just society.

From the beginning of the 16th century the traditional Catholic conception of man and of his relation to God and to the world had been assaulted by the rise of humanism, by the Protestant Reformation and by Age of Exploration, which brought on mistreatment of humans on a massive scale. These new problems were addressed by the School of Salamanca.

The leading figures of the school, theologians and jurists Francisco de Vitoria, Domingo de Soto, Martín de Azpilcueta (or Azpilicueta), Tomás de Mercado, and Francisco Suárez, were all scholars of natural law and of morality, who undertook the reconciliation of the new political-economic order and the teachings of Thomas Aquinas, who laid out the framework for human rights two centuries before. The themes of study centered on man and his practical problems (morality, economics, jurisprudence, etc.), but almost equally on a particular body of work accepted by all of them, as the ground against which to test their disagreements, including at times bitter polemics within the School.

The School of Salamanca in the broad sense may be considered more narrowly as two schools of thought coming in succession, that of the Salmanticenses and that of the Conimbricenses from the University of Coimbra. The first began with Francisco de Vitoria (1483–1546), and reached its high point with Domingo de Soto (1494–1560). The Conimbricenses were Jesuits who, from the end of 16th century took over the intellectual leadership of the Catholic world from the Dominicans. Among those Jesuits were Luis de Molina (1535–1600), the aforementioned Francisco Suárez (1548–1617), and Giovanni Botero (1544–1617), who would continue the tradition in Italy.

Francisco de Vitoria

The juridical doctrine of the School of Salamanca represented the end of medieval concepts of law, with a revindication of liberty not popular in Europe of that time. The natural rights of man came to be, in one form or another, the center of attention, including rights as a corporeal being (right to life, economic rights such as the right to own property) and spiritual rights (the right to freedom of thought and to human dignity).

The School of Salamanca reformulated the concept of natural law: law originating in nature itself, with all that exists in the natural order sharing in this law. Their conclusion was, given that all humans share the same nature, they also share the same rights to life and liberty. Mistreatment of American Indians and slaves were central political targets for the school.

Human Rights

Francisco de Vitoria was perhaps the first to develop a theory of ius gentium (the rights of peoples), and thus is an important figure in the transition to modernity. He extrapolated his ideas of legitimate sovereign power to society at the international level, concluding that this scope as well ought to be ruled by just forms respectable of the rights of all. The common good of the world is of a category superior to the good of each state. This meant that relations between states ought to pass from being justified by force to being justified by law and justice. Some scholars have upset the standard account of the origins of International law, which emphasises the seminal text De iure belli ac pacis by Grotius, and argued for Vitoria and, later, Suárez’s importance as forerunners and, potentially, founders of the field. Others, such as Koskenniemi, have argued that none of these humanist and scholastic thinkers can be understood to have founded international law in the modern sense, instead placing its origins in the post-1870 period.

Franciscus Suarez

Francisco Suárez subdivided the concept of ius gentium. Working with already well-formed categories, he carefully distinguished ius inter gentes from ius intra gentes. Ius inter gentes (which corresponds to modern international law) was something common to the majority of countries, although being positive law, not natural law, was not necessarily universal. On the other hand, ius intra gentes, or civil law, is specific to each nation.

Conquest of America

In this period, in which colonialism began, Spain was the only western European nation in which a group of intellectuals questioned the legitimacy of conquest rather than simply trying to justify it by traditional means.

Francisco de Vitoria began his analysis of conquest by rejecting “illegitimate titles”. He was the first to dare to question whether the bulls of Alexander VI known collectively as the Bulls of Donation were a valid title of dominion over the newly discovered territories. In this matter he did not accept the universal primacy of the emperor, the authority of the pope (because the pope, according to him, lacked temporal power), nor the claim of voluntary submission or conversion of the Native Americans. One could not consider them sinners or lacking in intelligence: they were free people by nature, with legitimate property rights. When the Spanish arrived in America they brought no legitimate title to occupy those lands and become their master.

Vitoria also analyzed whether there were legitimate claims of title over discovered lands. He elaborated up to eight legitimate titles of dominion. The first and perhaps most fundamental relates to communication between people, who jointly constitute a universal society. Ius peregrinandi et degendi is the right of every human being to travel and do commerce in all parts of the earth, independently of who governs or what is the religion of the territory. For him, if the “Indians” of the Americas would not permit free transit, the aggrieved parties had the right to defend themselves and to remain in land obtained in such a war of self-defense.

The second form of legitimate title over discovered lands also referred back to a human right whose obstruction is a cause for a just war. The Indians could voluntarily refuse conversion, but could not impede the right of the Spanish to preach, in which case the matter would be analogous to the first case. Nonetheless, Vitoria noted that although this can be grounds for a just war, it is not necessarily appropriate to make such a war, because of the resulting death and destruction.

The other cases of this casuistry are:

  • If the pagan sovereigns force converts to return to idolatry.
  • If there come to be a sufficient number of Christians in the newly discovered land that they wish to receive from the Pope a Christian government.
  • In the case of overthrowing a tyranny or a government that is harming innocents (e.g. human sacrifice)
  • If associates and friends have been attacked—as were the Tlaxcaltecas, allied with the Spanish but subjected, like many other people, to the Aztecs—once again, this could justify a war, with the ensuing possibility of legitimate conquest as in the first case.
  • The final “legitimate title” although qualified by Vitoria himself as doubtful, is the lack of just laws, magistrates, agricultural techniques, etc. In any case, title taken according to this principle must be exercised with Christian charity and for the advantage of the Indians.

This doctrine of “legitimate” and “illegitimate” titles was not agreeable to Emperor Charles V, then ruler of Spain, in that they meant that Spain had no special right; he tried without success to stop these theologians from expressing their opinions in these matters.


Luis de Molina

Murray Rothbard called the School of Salamanca proto-Austrians, noting their similarity to the Austrian School of economics. They understood basic principles of economics and were light years ahead of their time.

The most complete and methodical developments of a Salamancan theory of value were by Martín de Azpilcueta (1493–1586) and Luis de Molina. Interested in the effect of precious metals arriving from the Americas, de Azpilcueta proved that in the countries where precious metals were scarce, prices for them were higher than in those where they were abundant. Precious metals, like any other mercantile good, gained at least some of their value from their scarcity. This scarcity theory of value was a precursor of the quantitative theory of money put forward slightly later by Jean Bodin (1530–1596).

Up until that time, the predominant theory of value had been the medieval theory based on the cost of production as the sole determinant of a just price (a variant of the cost-of-production theory of value, most recently manifested in the labor theory of value). Diego de Covarrubias and Luis de Molina developed a subjective theory of value and prices, which asserted that the usefulness of a good varied from person to person, so just prices would arise from mutual decisions in free commerce, barring the distorting effects of monopoly, fraud, or government intervention. Expressing this in today’s terms, the adherents of the School defended the free market, where the fair price of a good would be determined by supply and demand.

On this Luis Saravia de la Calle wrote in 1544:

Those who measure the just price by the labour, costs, and risk incurred by the person who deals in the merchandise or produces it, or by the cost of transport or the expense of traveling…or by what he has to pay the factors for their industry, risk, and labour, are greatly in error…. For the just price arises from the abundance or scarcity of goods, merchants, and money…and not from costs, labour, and risk…. Why should a bale of linen brought overland from Brittany at great expense be worth more than one which is transported cheaply by sea?… Why should a book written out by hand be worth more than one which is printed, when the latter is better though it costs less to produce?… The just price is found not by counting the cost but by the common estimation.

However the school rarely followed this idea through systematically, and, as Friedrich Hayek has written, “never to the point of realizing that what was relevant was not merely man’s relation to a particular thing or a class of things but the position of the thing in the whole…scheme by which men decide how to allocate the resources at their disposal among their different endeavors.”

Property Rights

The adherents of the School of Valencia all agreed that property has the beneficial effect of stimulating economic activity, which, in turn, contributed to the general well being. Diego de Covarubias y Leyva (1512–1577) considered that people had not only the right to own property but—again, a specifically modern idea—they had the exclusive right to the benefit from that property, although the community might also benefit. Nonetheless, in times of great necessity, there all goods become a commons.

Luis de Molina argued that individual owners take better care of their goods than is taken of common property, a form of the tragedy of the commons.

Just War Theory

Given that war is one of the worst evils suffered by mankind, the adherents of the School reasoned that it ought to be resorted to only when it was necessary in order to prevent an even greater evil. A diplomatic agreement is preferable, even for the more powerful party, before a war is started. Examples of “just war” are:

  • In self-defense, as long as there is a reasonable possibility of success. If failure is a foregone conclusion, then it is just a wasteful spilling of blood.
  • Preventive war against a tyrant who is about to attack.
  • War to punish a guilty enemy.

A war is not legitimate or illegitimate simply based on its original motivation: it must comply with a series of additional requirements:

  • It is necessary that the response be commensurate with the evil; use of more violence than is strictly necessary would constitute an unjust war.
  • Governing authorities declare war, but their decision is not sufficient cause to begin a war. If the people oppose a war, then it is illegitimate. The people have a right to depose a government that is waging, or is about to wage, an unjust war.
  • Once war has begun, there remain moral limits to action. For example, one may not attack innocents or kill hostages.
  • It is obligatory to take advantage of all options for dialogue and negotiations before undertaking a war; war is only legitimate as a last resort.

Under this doctrine, expansionist wars, wars of pillage, wars to convert infidels or pagans, and wars for glory are all inherently unjust.


The School of Valencia distinguished two realms of power, the natural or civil realm and the realm of the supernatural, which were often conflated in the Middle Ages through granting royal control of investiture of bishops, or the temporal powers of the pope. One direct consequence of the separation of realms of power is that the king or emperor does not legitimately have jurisdiction over souls, nor does the pope have legitimate temporal power. This included the proposal that there are limits on the legitimate powers of government. Thus, according to Luis de Molina a nation is analogous to a mercantile society (the antecedent of a modern corporation) in that those who govern are holders of power (effectively sovereigns) but a collective power, to which they are subject, derives from them jointly. Nonetheless, in de Molina’s view, the power of society over the individual is greater than that of a mercantile society over its members, because the power of the government of a nation emanates from God’s divine power (as against merely from the power of individuals sovereign over themselves in their business dealings).

At this time, the monarchy of England was extending the theory of the divine right of kings—under which the monarch is the unique legitimate recipient of the emanation of God’s power—asserting that subjects must follow the monarch’s orders, in order not to contravene said design. Counter to this, several adherents of the School sustained that the people are the vehicle of divine sovereignty, which they, in turn, pass to a prince under various conditions. Possibly the one who went furthest in this direction was Francisco Suárez, whose work Defensio Fidei Catholicae adversus Anglicanae sectae errores (The Defense of the Catholic Faith against the errors of the Anglican sect 1613) was the strongest defense in this period of popular sovereignty. Men are born free by their nature and not as slaves of another man, and can disobey even to the point of deposing an unjust government. As with de Molina, he affirms that political power does not reside in any one concrete person, but he differs subtly in that he considers that the recipient of that power is the people as a whole, not a collection of sovereign individuals—in the same way, Jean-Jacques Rousseau’s theory of popular sovereignty would consider the people as a collective group superior to the sum that composes it.

Gabriel Vázquez (1549–1604) held that natural law is not limited to the individual, but obliges societies to act in accord and be treated with justice.

For Suárez, the political power of society is contractual in origin because the community forms by consensus of free wills. The consequence of this contractualist theory is that the natural form of government is either a democracy or a republic, while oligarchy or monarchy arise as secondary institutions, whose claim to justice is based on being forms chosen (or at least consented to) by the people.