Not to fuel this overmuch, but here are some distinctions.

I. Protestants believe God gives the Church public revelation (divinely revealed to the whole Church) through scripture. This is relatively stable. One believes what the Bible specifically teaches: no more, no less. Catholics/Orthodox believe that, as far as the NT is concerned, whatever Jesus happened to teach is revelation. This means there’s public revelation that isn’t recorded in the Bible, and we have to look at what early Christians wrote to deduce it.

II. Catholics/Orthodox believe that Church authority is derived by appointment through the bishops. In Catholicism a lot of that authority is vested specifically in the Bishop of Rome; the Orthodox place basically equal authority in their bishops. Protestants seem to believe that authority is derived from the people of the Church and from God, rather than organically through the Apostles. Authority in Protestantism arises naturally and through necessity.

III. Protestants view Christianity as a philosophy, and Catholics/Orthodox view Christianity as an institution. For Protestants, the essence of Christianity is a system of beliefs and actions set down in scripture: the tangible Church exists because it is part of this system (I should say, though, that the Reformed theologian Peter Leithart seems to want to move away from this model). For Catholics/Orthodox, the essence is the tangible Church. Doctrine, scripture, grace, and ritual are channeled through the tangible Church by God. The difference becomes clear in Lewis’ Mere Christianity, where he takes a typical and educated Protestant approach, and lays down the fundamentals of Christianity as a series of beliefs and ethical teachings; he speaks very little of the tangible Church.

What do you think? Have I been unfair to either side? Are the distinctions correct? Are they the fundamental ones?