C. S. Lewis, from “Membership”:

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 of 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. Thus, in a club, the committee as a whole and the servants as a whole may both properly be regarded as "members"; what we should call the members of the club are merely units. A row of identically dressed and identically trained soldiers set side by side, or a number of citizens listed as voters in a constituency are not members of anything in the Pauline sense. I am afraid that when we describe a man as "a member of the Church" we usually mean nothing Pauline; we mean only that he is a unit - that he is one more specimen of some kind of things as X and Y and Z. 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 incomensurables.