Of popes and power: in the middle ages, the Vatican reigned supreme.

In their effort to crack down on dissenting Catholic politicians in America, the Vatican and bishops may be feeling a little nostalgia for what they would consider "the good old days"--a period of several centuries when church authority in Europe was rarely successfully challenged.

Following the Christianization of the Roman Empire, Catholicism quickly spread and became Europe's dominant faith. For many centuries, it enjoyed a virtual religious monopoly. Popes often wielded temporal as well as spiritual power. In the frequent struggles between church and state, the church usually came out on top.

In a celebrated incident from 1076, for example, Pope Gregory VII and King Henry IV of England fell into a dispute over who should have the power to name church bishops--church leaders or government officials.

Gregory was so enraged by Henry's position that he excommunicated the king. Henry was forced to travel to Italy to the pope's winter castle at Canossa in the Italian Alps to beg forgiveness. Gregory kept Henry waiting outside in foul weather for three days before granting him an audience.

Later that year, Gregory bragged about his humiliation of the king, observing in a letter that Henry was "a pitiable figure who had laid aside all kingly attire and, as is natural for a penitent, was without shoes and clad in woolen garments."

Although Gregory granted Henry readmission to the church, four years later the two squabbled again. This time, Gregory not only excommunicated Henry but also took the additional step of ordering him from the throne and attempting to replace him with a German duke.

More than 100 years later, Pope Innocent III ordered various warring factions in Rome to cease hostilities and coalesce under his authority. Innocent insisted that all kings submit to the church and threatened to excommunicate any who disobeyed him. To Innocent, government leaders were simply instruments of furthering the church's goals.

When King John Lackland of England balked at the decree, Innocent wasted no time in proving that his words were no bluff. He excommunicated King John and placed all of England under "interdict"--a type of mass excommunication of an entire region or country.

Peasants feared interdiction, seeing denial of church services as a one-way ticket to eternal damnation. Facing withering pressure, King John was forced to give quarter and submit to Innocent. Innocent lifted the interdiction order, but only after John agreed to pay him a yearly fee.

Pope Boniface VIII in 1294 argued with French King Philip IV over Philip's plan to tax the church to pay for the king's wars. Boniface asserted that the church was required only to support crusades against the Muslims who held the Holy Land, not conflicts sparked by secular concerns such as squabbles over territory or trade.

In 1302, Boniface issued a papal bull, "Unam Sanctam," designed to end all doubt where the church stood in relation to secular governments. The decree bluntly states that all governments must submit to the church; it goes on to lay down the principle that anyone outside the church cannot expect salvation.

Asserts the bull, "We make simple confession that outside the Church there is no salvation or remission of sins.... We declare, affirm and define as a truth necessary for salvation that every human being is subject to the Roman pontiff."

The decree also codified an early vision of the church's view of church-state relations--the so-called "theory of two swords." Originally conceived by Pope Gelasius I (492-496), the theory envisions a society governed by two swords, one spiritual and the other temporal. But the two swords are not equal. The first is wielded solely by the church, and the second by civil government but on behalf of the church. Under this theory, spiritual power is supreme, not coequal, with temporal power.

The bull failed to persuade Philip. Boniface was preparing an order of excommunication when Philip sent soldiers to capture and imprison the pope. Friendly governments sent soldiers to Boniface's aid, but they were not needed. He was quickly released and died about a month later.

In 1864, Pope Pius IX issued the famous "Syllabus of Errors" that attacked the very idea of separation of church and state. But this hard-line attitude was softened by the Second Vatican Ecumenical Council under Pope John XXIII in 1962. During "Vatican II," as it is commonly known, the church endorsed the concept of religious liberty for everyone as a fundamental human right.

Some ultra-conservative Catholics have never been happy with Vatican II, considering it a cave-in to theological liberalism. These traditionalist Catholics pine for the absolute authority of the Middle Ages church. Given the church's waning public support in much of Western Europe and the resistance to clerical authority demonstrated by many American Catholics, a return to the "good old days" seems unlikely anytime soon.