This article affirms the importance of ecclesiastical polity as a theological–juridical discipline and explores its connection to ecclesiology and church law. It argues that the Anglican Communion, though not itself a church, nevertheless has a lightly structured ecclesiastical polity of its own, mainly embodied in the Instruments of Communion. It warns against short-term, pragmatic tinkering with Church structures, while recognising the need for structural reform from time to time to bring the outward shape of the Church into closer conformity to the nature and mission of the Church of Christ. In discussing Richard Hooker's contention that the Church is a political society, as well as a mystical body, it distinguishes the societal character of Anglican churches from the traditional Roman Catholic conception of the Church as a societas perfecta. In the tradition of Hooker, the role of political philosophy in the articulation of ecclesiology and polity is affirmed as a particular outworking of the theological relationship between nature and grace. The resulting method points to an interdisciplinary project in which ecclesiology, polity and church law, informed by the insights of political philosophy, serve the graced life of the Church in its worship, service and mission.

How can we explain the fact that the Anglican Covenant divides people of equal integrity and comparable wisdom around the world? We need to ask whether we have correctly understood both the ecclesiology of the Anglican Communion and the terms of the Covenant. What is implied in being a Communion of Churches, where the churches are the subjects of the relationship of communion (koinonia)? What does the Covenant commit its signatories to and, in particular, what does it say about doctrinal and ethical criteria for communion? Is it legitimate to apply biblical covenant language, in which the covenant relationship is between God and Israel, to relations between churches? By addressing some of the concerns of those who oppose it, a case is made in favour of the Covenant and some reassurances are offered. In conclusion, the mystical dimension of being in communion is affirmed.

The effect of the presence of diamondlike carbon coatings deposited on (100) Si substrates on the deformation mechanisms operating in the silicon substrate during contact loading have been investigated by both cross-sectional transmission electron microscopy and modeling of the stresses generated beneath the indenter tip. The observed subsurface microstructures were correlated to the Tresca shear stress and the hydrostatic stress generated in the silicon substrate beneath the indenter tip. The presence of the coating altered the stresses generated in the substrate, and changed the deformation mechanism from one of principally phase transformation in uncoated Si to predominantly dislocation motion in the silicon substrate for the diamondlike C–Si system. The magnitude and distribution of the shear and hydrostatic stresses in the substrate were found to depend on both the indentation load and the thickness of the coating. Furthermore, the observed width of deformation, parallel to the interface, which was found to increase with coating thickness, was correlated to the wider distribution of the Tresca shear stress in the substrate brought about by the presence of the coating.