Prof Schillebeeckx is concerned with three things: an ongoing, living, community-based Christian faith; openness towards science and scientific method; and an effective Christian praxis. How are these related? Its is the problem of faith and reason with the addition of a third element, action. Under the heading 'reason' come linguistics and Jurgen Habermas's critical theory of society; and this last, neo-Marxist theory presses on Christianity the question of the relation between faith and action in our world.