The obvious objection to a council of churches is that joining one looks like conceding the argument. If an episcopal church that holds valid orders to be necessary sits down as an equal member with a church it regards as lacking them, has it not admitted that the question does not matter?
The council answered this two years later, at Toronto, in a statement that made the whole enterprise workable. Membership in the World Council does not imply that a church regards the other member churches as churches in the true and full sense of the word. It does not imply that any doctrine of the church is being accepted, or that relativism about doctrine is being adopted. Each church retains its own understanding of what the church is and of where it is found.
That formulation is what lets bodies that deny each other's orders, sacraments and ecclesial standing sit in the same room and work together without either side conceding anything. It is a negative agreement, an agreement about what agreement is not being reached, and it has held for three quarters of a century.
The membership has grown well beyond 1948. Most of the Orthodox churches came in later, the Russian Orthodox Church at the New Delhi assembly of 1961, and the centre of gravity has moved decisively towards Africa and Asia. The Roman Catholic Church has never been a member. It sends observers, works with the council on particular commissions, and has consistently declined to join a body whose basis of membership is deliberately less than its own understanding of the church.