The Anabaptists took a very different approach to mission than the Celtic Church. The Celtic church evangelised with sensitivity to context and culture, even incorporating some cultural traditions into the church. Anabaptists believed that the rest of the world, including the established church, was essentially Pagan and preached the gospel with the expectation that people convert and get baptised.
The Celtic church was a territorial model of church, where everyone within a geographical location belonged to the church, but the Anabaptists believed that you had to be baptised to belong to the church, demonstrating a model of gathered church, rather than territorial.
The Anabaptists were more counter-cultural in their approach to mission, where the Celtic church incorporated common culture to make themselves relevant.
The Celtic church was very active in planting monasteries all across Europe, with the idea that they were territorial, and that everyone within the ‘Parish’ belonged to the church.
The Anabaptists approach to mission was to plant new churches that would house new converts and baptise them, making them members of that church. A very new approach to mission for the church.