The very word membership is of Christian origin, but it has been taken over by the world and emptied of all meaning. In any book on logic you may see the expression “members of a class.” It must be most emphatically stated that the items or particulars included in a homogeneous class are almost the reverse of what St. Paul meant by members. By members. . . .he meant what we should call organs, things essentially different from, and complementary to, one another, things differing not only in structure and function but also in dignity. . . . . How true membership in a body differs from inclusion in a collective may be seen in the structure of a family. The grandfather, the parents, the grown-up son, the child, the dog, and the cat are true members (in the organic sense), precisely because they are not members or units of a homogeneous class. They are not interchangeable. Each person is almost a species in himself. The mother is not simply a different person from the daughter; she is a different kind of person. The grown-up brother is not simply one unit in the class children; he is a separate estate of the realm. The father and grandfather are almost as different as the cat and the dog. If you subtract any one member, you have not simply reduced the family in number; you have inflicted an injury on its structure. Its unity is a unity of unlikes, almost of incommensurables.
A dim perception of the richness inherent in this kind of unity is one reason why we enjoy a book like The Wind in the Willows; a trio such as Rat, Mole, and Badger symbolises the extreme differentiation of persons in harmonious union, which we know intuitively to be our true refuge both from solitude and from the collective.
—from “Membership” (C. S. Lewis – The Weight of Glory)