“Doctrine that all relations are internal to their bearers, in the sense that they are essential to them and the bearers would not be what they are without them. Some relations are clearly internal in this sense (four would not be four unless it were related to two by being its square), and some relations are internal to their bearers under one description but not under another (a wife would not be a wife unless suitably related to a husband, but Mary would still be Mary had she not married). The doctrine that all relations are internal implies that everything depends on everything else for being what it is, and is therefore associated with monistic or OBJECTIVE IDEALISM.”
G.E. Moore, “External and Internal Relations,” Proceedings of the Aristotelian Society (1919-1920); reprinted in G.E. Moore, Philosophical Studies (1922).