Children's vulnerability asks for people taking up responsibility for children. In this contribution, three different ways of thinking on foundations of (ethical and spiritual) responsibility for children are discussed, namely, a liberalist, a social-constructivist and a naturalist paradigm. The author argues that cultural and natural elements are important in the reflection on responsibility, that is, the social-culturally determined way in which one looks at children plays a role, but responsibility is never totally dependent of these cultural ideas. The idea of "heteronomous responsibility" is developed. Theories cannot guarantee that parents take up their responsibility, but a parental promise can be made. (Contains 1 note.)