The phenomenal population increase of the second half of the twentieth century presents Christians with exciting problems of construction. The difficult but necessary break with the architectural conventions of past centuries in the adaptation of places of worship to the idea of modern art has concentrated the attention of worshipers and constructors on technical and aesthetic matters. It has too often diverted their attention from those essential considerations which should be uppermost in the building of a Christian Church. The interior arrangement of the church is the outward expression of the chief architect's theological understanding of the community's relationship with God. There are unfortunately far too many sanctuaries which betray the fact that such understanding is often absent. The constructors passively submit to all kinds of hidden pressures, to conventions, to unconscious custom and to religious traditions which are quite foreign to the Christian faith. The subject of this study is restricted to the conception of the interior arrangement of Christian sanctuaries, and in particular to the architectural plan of churches, taking note of historical and theological relationships to reformed worship. - Introduction.