Finland sits on a religious fault line that runs through the country rather than around it. Western Finland was drawn into the Latin church through Swedish rule from the twelfth century and into Lutheranism with Sweden in the sixteenth. Eastern Karelia was drawn into the Orthodox world through Novgorod, and the monasteries of Valaam and Konevitsa on Lake Ladoga were its centres. The border between those two spheres moved repeatedly, and it moved again in 1940, when the ceded territories were evacuated and the monks of Valaam carried their community into Finland to refound it as New Valamo at Heinavesi. The Finnish Orthodox Church is small, around one per cent of the population, but it is a national church in law alongside the Lutheran one, and both may levy a church tax collected by the state.
The Lutheran church still holds a majority of Finns as members, though the share has fallen steadily and resignations rose sharply once an online service made leaving straightforward. Attendance is low, but the rites of passage held: a large proportion of fifteen year olds still attend confirmation camp, which functions as much as a social institution as a religious one.
Northern Finland is different again. Laestadian revivalism, named for the Swedish Sami botanist and preacher Lars Levi Laestadius, spread through the north from the 1840s and remains a substantial movement within the Lutheran church rather than outside it. Its largest branch, Conservative Laestadianism, is one of the few groups in the Nordic countries with high birth rates and high observance, and its internal disputes are national news.