The Inquisition, understood as the research into religious creeds, was not an exceptional or abnormal phenomenon peculiar solely to the Middle Ages, but rather an imperious function of government observed across antiquity, the Middle Ages, and the Renaissance.

Society, being based on religion, universally necessitated its protection and fostering in the public interest.

A change in religious belief was often seen to lead necessarily to social transformation, with political revolutions being the practical application of philosophical theories that were potentially hostile.

Thus, the principle that both human and divine law ought to be respected became established. Despite its often tyrannical and sanguinary excesses in attempting to impose religious conviction, some individuals of noble views and generous sentiments protested against such methods.

Ancient Precedents

The concept of inquiring into religious orthodoxy existed among the Greeks, as evidenced by the accusation against Socrates, which led to his death on the grounds that he did not recognise the gods of the republic.

In Rome and Athens, there was a prevalent suspicion and mercilessness towards those who refused to venerate the state gods, resulting in cruel persecutions and the martyrdom of thousands under Roman emperors.

Christians sought refuge in the Catacombs for prayer and holy mysteries, but their religious beliefs, being contrary to the State, were unpardoned. They faced death if they refused to offer incense to the republic's gods.

Emperor Trajan, for instance, stated that Christians were not to be actively sought out, but if denounced and unwilling to change their faith, they were to be punished. An example is Saint Cecilia, a Roman patrician, and her family, who, despite their distinguished birth and wealth, were arrested and condemned to death for their refusal to sacrifice to false gods. Similar events were recorded in Gaul and the East.

The Papal Inquisition

Following the conversion of Constantine, the secular arm began to serve the Church in upholding the unity of faith. However, the civil power's ambition to exert sovereign influence over religious trials led to regrettable abuses.

The Italian Inquisition, under the direct guidance of the popes, emerged in the fifth century. Pope Leo, after investigating Manicheans who had sought refuge in Rome, affirmed that the Inquisition must persist not only to encourage the devout but also to convert those who had strayed. The primary goal of the Inquisition was to identify and halt the spread of doctrinal errors, and to enlighten and reclaim those corrupted by false teachings.

In the twelfth century, Pope Lucius III., aiming to curb the advancement of Manicheans (known also as Catharists or Waldenses), mandated that bishops visit suspected areas of their dioceses once or twice annually.

Heretics were to be reported and summoned by the bishop to renounce their heresies or face canonical penalties. Religious error was thus perceived as an offence against public order, and princes regarded heretics as rebels.

This was consistent with the prevalent ideas of the Middle Ages, where the entire social fabric rested upon the Catholic faith. It is notable that the Roman Inquisition, while being the earliest and enduring beyond the Middle Ages, was also considered the most moderate, as it never mandated capital punishment.

The Inquisition in France

The Inquisition was introduced into France due to an Eastern heresy that blended Pagan Armenian Manicheism with Christian ceremonies, originating and focusing in Toulouse and Albi, giving rise to the name Albigenses.

Despite previous efforts, this heresy continued to proliferate across the southern French provinces, attracting adherents even among the clergy and nobility. Pope Innocent III., elected in 1198, became alarmed and sought to compel these sectaries, who were openly supported by powerful counts and viscounts, to obedience, initially through persuasion.

Monks Guy and Raynier were the first commissioners of the Holy See to be termed inquisitors.

Their lack of success prompted Innocent III. to grant full powers to Peter de Castelnau and Ralph, who, along with Abbot Amalric, preached against the Albigensian heresy, yet the heretics showed greater resolve.

Dominic Guzman, a Spanish prelate known for his gentleness, zeal, and piety, also preached against the heresy but was similarly unsuccessful and faced public insult. The assassination of legate Peter de Castelnau by esquires of Raymond VI., Count of Toulouse, in 1208, led Innocent III. to initiate a new crusade against the Albigenses. Béziers was stormed in July 1209, leading to the massacre of 20,000 inhabitants and the burning of 7,000 in a church.

Simon de Montfort led the military campaign, stripping the Count of Toulouse of his domains. Louis VIII. supported rigorous measures, including a decree from the Bishop of Toulouse mandating a fine for every Waldensian discovered and the destruction and confiscation of property associated with them.

Dominic, the founder of the Order of Preaching-Brothers (Dominicans), employed spiritual methods against heresy, notably introducing the rosary. He delegated his order's provincials to preach against heresy across Europe. Raymond VII. was later reconciled with the Church, and his daughter's marriage secured the transmission of his lands to the French crown. King Louis IX. reinforced these efforts with a ten-clause decree aimed at repressing heresy through the secular clergy, which included enforcing tithe payments and compelling the excommunicated to return to the Church via seizure of goods. Consequently, the Inquisition's presence in France became less critical, and its activities in Toulouse were suspended in 1237.

The Royal Spanish Inquisition

In Spain, the Inquisition was primarily royal rather than papal.

This context is vital, given Spain's seven-century struggle for independence against the Moors and Jews, who, despite feigning conversion, harboured deep antipathy towards Christianity.

Ferdinand and Isabella, aiming to safeguard national unity, considered religious unity essential, leading them to order Moors and Jews to convert or leave the country.

They established a special Inquisition directly under their control. The popes initially protested this claim to superintend the Inquisition, with Pope Sixtus IV. recalling his legate, though a bull eventually legalised the Spanish Inquisition. Sixtus IV. later regretted its excesses, and Spanish monarchs attempted to obstruct appeals to Rome. Popes resorted to stratagem to protect penitent heretics, issuing secret absolutions, which were not always approved by the Spanish government. Leo X. even excommunicated the Inquisitors of Toledo, and Charles V. used the pretext of Lutheran reform to prevent papal interference.

The Spanish Inquisition was supported by three corporate bodies: the Holy Hermandad (police officers who became a military force), the Cruciata (archbishops and bishops enforcing Church laws), and the Militia of Christ (a military order assisting the Inquisitors). By 1481, with new regulations, it became formidable, primarily targeting Jews and Moors who relapsed into Paganism.

It was renamed The Holy Office and overseen by a grand inquisitor-general and a council called The Supreme, comprising forty-five members.

Upon arrest, the accused was stripped, and an inventory of their belongings was made for restoration if found innocent, though seized money was taken for tribunal costs. Prisons included common, mercy/penitence (temporary), intermediate, and secret (solitary confinement).

Trials took place in a black-hung hall with a crucifix, where the Inquisitor-general presided, flanked by other inquisitors, a secretary, spies, and four masked men. If the prisoner did not confess after a long interrogation, they were subjected to torture, using methods like the cord, scourge, fire, or water, similar to civil tribunals.

Judgments were pronounced in a ceremony known as the Auto-da-fé, or Act of Faith.

The procession included Dominicans carrying the Holy Office banner, inscribed with Justitia et misericordia, followed by the condemned, spies, and the executioner. Penitents wore specific garments called san-benitos, with variations indicating the nature of their repentance and punishment.

For instance, those reconciled before sentence wore yellow scapularies without flames, while those condemned to burning who later recanted wore scapularies with downward flames, signifying strangulation before burning. Impenitent individuals wore san-benitos with upward flames and demonic figures, indicating burning alive.

The ceremony occurred in a church, with a black-draped altar and special daises for the Inquisitor and royalty. After the reconciled made their abjurations, the impenitent were handed to secular power. Although executions sometimes followed, many Auto-da-fés, such as those in Toledo in 1486, saw public penance but no bloodshed, with only a small fraction of penitents ultimately executed.

The Spanish Inquisition's jurisdiction extended beyond heresy to various crimes including unnatural acts, brigandage, sacrilege, usury, murder, and sorcery. The political objective of maintaining religious unity was achieved, preventing the bloody revolutions seen in other European nations.

The Inquisition in the Netherlands

The Inquisition was less effective in the Netherlands, where Protestantism gained ground under Charles V.. The nobility and clergy, angered by Philip II.'s harsh anti-heresy measures, supported a general uprising against the Spanish.

Protestants took up arms, burning churches, massacring clergy, and suppressing Catholic worship. The Duke of Alva's establishment of the council of troubles, nicknamed the council of blood, transformed the religious issue into a struggle for national independence, resulting in the separation of the United Provinces (Holland) from Catholic Belgium.

The Protestant Inquisition

Upon forming the United Provinces, despite their principle of free inquiry, an instinctive drive for religious unity led them to surpass Spain in devising tortures for Catholics who refused to convert.

Persecution also erupted between different reformed Churches (Calvinists and Lutherans) for the sake of state stability. In Saxony, for example, the Calvinist chancellor Crell was imprisoned and later beheaded by rigid Lutherans. In Brunswick, Lutheran preachers justified executions from the pulpit, even as gibbets remained displayed.

In the southern French provinces, where the Reformation gained dominance, the Huguenots committed excesses, torturing Catholics by chaining them to induce cannibalism, dragging them naked along ropes to cut them in half, or slowly burning them at stakes.

In England, Henry VIII.'s efforts to enforce religious unity through extreme violence, including the executions of high-ranking figures like Chancellor Thomas More and the Bishop of Rochester, transformed his court into a slaughter-house.

Switzerland also experienced severe forms of Inquisition under Calvin in Geneva. Calvin allowed disparaging terms for opponents, while peasants were imprisoned for rough language, and children whipped for minor transgressions.

One hundred and fifty persons were burned as sorcerers in sixty years, and speaking ill of Calvin was a capital offence.

Calvin explicitly threatened Michael Servetus, a medical practitioner and theologian, and after Servetus's arrest and escape, he was later apprehended in Geneva by Calvin's spies and burnt alive in 1553.

Calvin's actions were endorsed by other cantons and Melancthon, though Protestant historians later deplored the loss of Geneva's traditional liberties.