Quick answer: Faith comes from sermons, and sermons need the church, which stays locked until you finish Jack's boat quest. Help Jack build his boat (5 Wooden Planks + 5 Bronze Details), get the twins to row it (Twins quest), wait a few days for Jack's letter, then talk to the nun at the village tavern. Clean the church and add benches until it has enough holiness, then hold a sermon once a week on Wrath day. Each sermon pays the smaller of your Town Gratitude and your church rating.
This page covers how to get faith, how to open the church, Glauben and how much faith does the priest give — the one quest line most players say they should have started sooner.
Steps
Start Jack in a Boat
After you meet the twins south of the village, Jack turns up near your house. Bring him 5 Wooden Planks and 5 Bronze Details (research Woodworking I and Bronze Works first).
Get the twins to row
Finish Two Peas in a Pod (6 Clay Plates). Once the boat is ready and the twins agree to row, Jack sails away.
Meet the nun
A few days later Jack's letter arrives. Go to the village tavern and talk to the nun; she unlocks the church next to your graveyard.
Fix up the church
Clear the rubble and build interior benches until the holiness meter (top right) is high enough. In the 100-day run it went "from negative to positive… 10 out of 10".
Hold a sermon on Wrath day
Once a week. You get Faith and some money. Improve the church with shrines, candles and incense from the Theology branch, and write better sermons as your writing mastery rises.
Why a sermon gave almost no Faith
The payout is capped by whichever is lower: your Town Gratitude or the church rating. Aim for at least 10 Gratitude before each sermon. Too many zombies (Excessive zombies debuff) also cuts the payout — see Zombies.
Nun's quest won't finish?
Two causes players found on Steam:
- Choir built too early. If you built the zombie choir before accepting the nun's choir quest, the quest doesn't register it. There's no confirmed workaround yet — if you haven't built it, accept the quest first.
- Nun's affection stuck at 20. Her next quest (stopping the donkey's corpse deliveries) only triggers when your morgue is full — let bodies pile up.
What Faith is for
Studying items at the Study Table, unlocking fast-travel milestones (start with the village and the port), perks, Herbert's early quest (he wants 3 Faith) and resurrecting zombies.
Related
Sources: a 7-tips guide, a recorded 100% playthrough and a 100-day playthrough on YouTube, GamesHorizon, Prima Games.