Ancient thought subordinated man to a divine cosmos, that is, to a perfect universe of which he was merely a part. Monotheism, on the other hand, asserts the infinitely superior value of man over nature, insofar as man is created in the image of God. This crucial point is at the origin of a true ethical revolution. The Bible affirms the sacred and infinite value of each human being.

This is why biblical ethics change our relationship to evil. It brings a sharp and unprecedented sensitivity to human suffering. It therefore encourages us to consider as abnormal and unbearable evils that humanity had previously found perfectly bearable, especially the evil done to others, the weak, and the innocent.

Symmetrical ethics is about establishing strict equality in human relationships or strict reciprocity. It appears in the virtue of justice, the supreme virtue for the Greeks. Justice is giving to others what is owed to them: to each their own—perceiving time as cyclical leads to a sense of not being responsible for the evil done by others. There is evil on Earth, but it has always existed and will always exist. This must be chalked up to the profit and loss account, and the sum of it is constant. There is nothing to be done, it will always be so, this is Greek and Roman fatalism.

Biblical ethics are asymmetrical, meaning that one must give more than what is owed. Everyone feels responsible for evil, even for that which they have not committed—ethics of giving, ethics of forgiveness, ethics of compassion. One cannot remain indifferent to the suffering of others and must not tolerate gratuitous suffering, even when it does not come from us. The tranquillity of the Stoic sage who accepts fate becomes impossible. This is the meaning of the parable of the Good Samaritan. Nothing obliges him to stop and take care of a man wounded by bandits. From the ethical revolution brought by the Bible, all of humanity becomes a sort of Good Samaritan. It is invited not to tolerate the evil done to others and to fight against it. Moreover, since God is the creator, we see the emergence of a new concept: the equality of all before God. There are no privileged individuals in the face of the transcendent immensity of God, and all men are equal.

The most well-known incarnation of this emerging doctrine is the School of Salamanca, located in Spain during the 16th century. Francisco de Vitoria, one of its representatives, asserts that if every man is created in the image of God, no man can be declared inferior to another, not the Jew, nor the black slave, nor the Indian.

The discovery of the Americas constituted a real cultural shock, a first breach in the politico-religious unanimism inherited from Antiquity. The famous controversy over the rights of the Indians indeed divided theologians into two opposed and irreconcilable camps.

In one camp, there were the proponents of cultural monolithism and the principle of coercion. For them, the Indians lived outside the biblical message. This could mean that God did not want to reveal Himself to them. Why? Two hypotheses are then conceivable: 1° They are great sinners (cannibalism), 2° They are backward and closer to the beast than to man. That's why they have the right to treat them as slaves and take their lands by force, because they are both infidels and barbarians.

In the opposing camp, there were the proponents of pluralism and civil liberties, including the theologians of the School of Salamanca, disciples of St. Thomas. According to Francisco de Vitoria and Bartolomeo de Las Casas, rights must be recognized for the Indians as human beings, not because they have adhered to or not adhered to the Catholic faith. Not only should they not be converted by force, but their possessions should not be taken, nor should they be subjected to any form of slavery. Their argumentation is based on the Thomistic conception of natural law, distinct from divine law.

In the Summa Theologica, St. Thomas poses the following question: Should one obey an unfaithful Prince who does not believe in God? And he answers yes, because legitimate authority is by natural right, and the Prince's infidelity or atheism is not a reason for rebellion. The political order is primarily a natural order. He further asks: Should war be waged on the infidels and the faith imposed on them? He answers no: a war is just only if it is defensive. Finally, faith can only be a free act. The scholars of Salamanca applied this reasoning to the case of the Indigenous peoples, arguing that property is a natural right. Therefore, taking lands from the Indigenous peoples is to commit theft, just as if they were Christians. It is also not permissible to wage war on them, given that there is no aggression on their part, but rather from ours.

The matter of the Indigenous peoples was the first crack in the politico-religious monolith. It showed that the unity of the political society could rest on a basis other than the religious unity of the inhabitants of the same territory, based on a common bond rooted in human nature.

The idea of humanity progresses. It effectively came to be considered that there is only one humanity to which equal rights are naturally linked. But it will still take time for it to be accepted by all. This will notably require the contribution of the natural sciences to the concept of the human species.