Confessionalism, in a religious (and particularly Christian) sense, is a belief in the importance of full and unambiguous assent to the whole of a religious teaching. Confessionalists believe that differing interpretations or understandings, especially those in direct opposition to a held teaching, cannot be accommodated within a church communion.
Confessionalism can become a matter of practical relevance in fields such as Christian education and Christian politics. For example, there is a question over whether Christian schools should attempt to enforce a specific religious doctrine, or whether they should simply teach general "Christian values". Similarly, some Christian political parties have been split over whether non-Christians should be allowed to participate — confessionalists, arguing against it, stress the importance of religious doctrine, while non-confessionalists say that shared values are more important than adherence to exact beliefs.
Historically, the term confessionalism for the first time was used in mid-19th century. Of course the phenomenon of confessionalism and the term “confession”, from which the term confessionalism derived, is much older, referring to once individual belief, then collective belief. Furthermore, the term confession in different languages implies different notions (faith, denomination, croyance, culte, communauté religieuse).
In the 16th and 17th centuries the term confession was only used for the documents of belief (cf. Confessio Augustana) while the religious communities of Roman Catholics, Lutherans, and Calvinists were referred to as “religious parties”, different “religions” or “churches” - not as confessions. In the late 18th century the term confession started to expand to religious bodies sharing a common creed. The first evidence is the Wöllner and Prussian Religious Edict of 1788 (though there might be earlier proofs for the English-speaking world). The international Congress of Vienna in 1815 still didn’t use the term confession to mark different Christian denominations. Labelling Christian groups “confessions” implied a certain degree of civil progress and tolerance, accepting that no party could claim absolute truth. The original intention to pacify conflicts between the denominations in the 19th century turned into its opposite: Confession bore the ground for new conflicts, as for example in the Cologne conflict about mixed marriages in 1837. The Roman Catholic Church refused to consider itself as merely a confession.