Orthodoxy vs Heresy
That's just a fancy way of saying that the initial conflict was between what the Roman Catholic Church taught and what the group we know as Cathars taught.
Even with primary documents it is difficult to sort out what the Bons Hommes (Good Men) and Bonnes Femmes (Good Women) or simply Bons Chrétiens (Good Christians), as they called themselves, believed. That's because their beliefs come down to us through the writings of their enemies, and the Catholic Church leaders tended to lump all heretics together, intermingling, confounding, and conflating their beliefs into a stew from which they could draw out the bits they believed most damning with which to accuse their enemies.
Let's pull back for a moment.
'Heresy' is defined as 'adherence to a religious opinion contrary to church dogma; denial of revealed truth by a baptized member of the Roman Catholic Church.' (Merriam-Webster Online) 'Orthodoxy' means belief or practice that conforms to established doctrine of the church. In medieval Europe, that meant established teachings of the Roman Catholic Church.
From its earliest days, the organized Christian Church dealt with diverse opinions on theological subjects such as the relationship between God the Father and God the Son, the nature of Jesus, and the relationship between faith and works in salvation. In the 1050s AD, the Church split between East and West over, among other things, the Filioque, or 'and the Son' in the Creed. The Western (Catholic) Church maintained — and still maintains — that the Holy Spirit proceeds from the Father and the Son. The Eastern (Orthodox) Church held and holds that the Holy Spirit proceeds from the Father. Period.
The heresies of the twelfth century — and there were many — were different to at least some degree and grew out of a number of factors, philosophical, political, social, and organizational. Many heresies were small movements that grew up in reaction to clerical abuses and from an attitude of anti-clericalism. Some names are known to us today.
Three heresies, however, stand out because of their widespread popularity: Bogomilism, Waldensianism, and Catharism. Since Bogomilism arose in modern Bulgaria in the tenth century and was most active in the East, we won't consider it here.
Waldensianism arose when Peter Waldo (Pere Valdes in his native Lyonnaise French), a merchant, took vows of poverty and began to proclaim Church doctrine as a layman. The difference between his lifestyle and that of the priests and bishops was stark. Others took note, and his group became a movement in the late 1100s. Eventually, Peter and his followers called for a return to the simplicity of the early Church, preached clerical reform, and became a threat to the established order. The Church declared them heretics but was unable to eradicate them despite severe and widespread persecution into the 18th century.. Waldensian churches exist today and fall into the general classification of 'Protestant.'
For more information, visit the website of the American Waldensian Society.
What we know as Catharism spread significantly farther than Waldensianism, being found throughout the Holy Roman Empire, the Kingdom of Sicily, and in the Byzantine Empire. Its popularity posed a genuine threat to the hegemony and power of the Roman Catholic Church. The success of Catharism would have ended the universal, unified Western Church long before Martin Luther and the Protestant Reformation.
To learn more, visit The Rise of Popular Heresies and Popular Heresy in the 12th Century.
In my book, Chevalier: A Time for War, I present what are commonly considered the primary beliefs of the people we call Cathars, as well as their lifestyle. (All pronouncements made by Cathar figures in the book represent either statements made by Cathars or positions attributed to them by scholars.) The combination of teachings and lifestyle presented a powerful challenge to the power and authority of the Roman Catholic Church. The 'believers' (as they called the laity) as well as the 'Good Men" and 'Good Women' considered themselves Good Christians hoping to return the Church to its ancient and pure teaching and form.
So, what was Catharism?
If we believe what their opponents wrote about them, the Cathars followed dualism. Dualism represents the idea that two entities or powers account for the world as it stands. In Christianity, we have to distinguish between absolute (or radical) dualism and mitigated dualism.
Absolute dualism proposes two equal and eternal powers or gods. For example, God and the Devil. According to this view, the Devil (or Satan) is not a created being who rebelled but a second god equal and in opposition to God. This carries the name bitheism or ditheism.
Mitigated dualism asserts that the second power or god is lesser than the Supreme God and not necessarily co-eternal. Many people see the orthodox Christian teaching about the devil (Satan) as mitigated dualism. The Bible makes it clear that Satan, the accuser, is subject to and less powerful than God (cf. Job 1–2; Revelation 12; Revelation 20).
Cathar teaching included a dualism between matter and spirit. They were reported as teaching that matter was evil because the evil god, the 'King of thoed as teaching that matter was evil because the evil god, the 'King of thiis World' (cf. 2 Corinthians 4:4 — "the god of this world") created it. God, the good god, later revealed the world of the Spirit through Jesus.
Obviously, this matter-spirit dualism lies at odds with the creation account in Genesis 1, in which God proclaims each part as well as the totality of creation to be 'good' and 'very good.' To what extent the two can be reconciled is a matter of debate.
Nor do we know to what extent the Cathars of Occitania believed this. We do know that they argued the physical sacraments could not make a person holy. Chevalier reflects this in the colloquy or debate Jaufre witnesses in Montréal. These pronouncements, their railings against the lavish extravagance of the Church, and the asceticism of the Good Men and Good Women (those who had taken the Consolamentum) give the impression that they considered the material world evil.
From the belief that the material world is inherently evil arise two widely divergent views and practices. On the one hand, this can lead to a rejection of all things material and an ascetic lifestyle. This was the choice of the Cathar 'Perfects.' On the other hand, a view that what one does 'in the flesh' has no bearing on the spiritual can lead to a lascivious and licentious lifestyle. This would have been anathema to the Cathars in their rejection of the luxurious and licentious lives of the 'princes of the Church.'
Cathar belief also led to a very egalitarian view of the sexes, thus making it quite appealing to women, who could become figures of distinction and influence. The attitude and practice stood in sharp contrast to the Catholic view of women as subject and subordinate to men.
In particular, the Cathar Church preached a return to 'apostolic simplicity.' They believed their view represented the purity of the early church's theology. Coupled with their simple lifestyle, involvement in the lives of others, and practical ministrations to the poor, infirm and sick, the Cathar Perfects and their teachings became extremely popular.
While the poor people embraced Catharism, the nobility permitted and occasionally embraced it, and the local clergy tolerated it, the Catholic hierarchy opposed it ferociously. The bishops, archbishops, cardinals, and pope, in particular Pope Innocent III, viewed Catharism as an existential threat to the Church.
At first, the papal curia sent preachers and legates to persuade people to abandon the heresy. They were ineffective because of the contrast between rich prelates who never gave the needs of the poor a second thought and the involvement of the Perfects. It is a powerful example of the maxim, "People must know that you care before they care what you know."
When even the most powerful preachers, including those who adopted a simple style of life, failed to make headway against the heresy, the Church took sterner measures. Papal legates and archbishops excommunicated the Cathar leaders and those who protected them. They preached violence. At last, Pope Innocent launched the Albigensian Crusade.
Resources
To learn more about the Cathars and the Albigensian Crusade, read the following:
Montaillou by Emmanuel LeRoy Ladourie. The book is based on meticulous records from the Inquisition of inhabitants in a remote Pyrenean village in the fourteenth Century. It, like all books, should be read critically.
Song of the Cathar Wars by William of Tudela (translated by Janet Shirley). Considered a primary source. It is, of course, biased.
History of the Albigensian Crusade: Peter of Les Vaux-de-Cernay's 'Historia Albigensis by W.A. Sibly and M.D. Sibly.
The Chronicle of William of Puylaurens by W.A. Sibly and M.D. Sibly.
There are, of course, many other works about the Albigensian Crusade, but these will take you closest to the primary source documents. Read them with the understanding that we still know little about the period and know it from the viewpoint of the victors. Much remains conjecture.