Hiebert developed several theories that widely influenced the study and practice of Christian missions. His model of "critical contextualization" describes a process of understanding and evaluating cultural practices in light of biblical teaching. It is one of the most widely cited models in evangelical doctoral dissertations dealing with contextualization. The concept of the "excluded middle" argued that most
Westerners see the universe as consisting of two tiers - the invisible things of the other world, and the visible things of this world. In this way, they exclude the part in between - namely, the invisible things of this world, and in particular the unseen personal beings, such as angels and demons. Hiebert suggested that non-Westerners are much more likely to accept this "excluded middle". Hiebert, who studied mathematics as an undergraduate, employed the idea of
set theory to describe
bounded sets versus centered or
fuzzy sets as different ways of conceiving Christian community and theology. == Selected bibliography ==