This title presents the first coherent exposition of Dumitru Staniloae's understanding of the Christian Church. This is an Ecumenical milestone. Widely considered the most important Orthodox theologian of the twentieth century, Dumitru Staniloae (1903-1993) contributed significantly to an ecumenical understanding of these themes. Because of his isolation by the Romanian Communist regime, his work still awaits its merited reception, especially given its potential contribution towards Christian unity. In Staniloae's understanding the Church is a communion in the image of the Trinity. Because there is a continuum of grace between the Trinity and the Church, the same relationships that exist among trinitarian persons are manifested in creation in general, and the Church in particular. In this way, the Trinity fills the world and the Church, determining their mode of existence. Intratrinitarian relationships are manifested in the relationships between humankind and non-human creation, the Church and the world, local and universal aspects of the Church, clergy and the people, and among various charisms. "Ecclesiological Investigations" brings together quality research and inspiring debates in ecclesiology worldwide from a network of international scholars, research centres and projects in the field.