And I also wonder about the remarkable similarity betwee the three marks of the true church (word, sacraments, … and discipline), and the three outward and ordinary means of grace (word, sacraments, … and prayer). Why isn’t prayer a mark of the true church? And why isn’t discpline an ordinary means of God’s grace to his church?
Now the three marks are spelled out in BC 29, but the three means are spelled out in SC 88–, LC 154– (but no marks in Westminster, nor means in the Three Forms, at least that I can find explicitly spelled out). Is it just a Continental vs. Westminster thing — different ways of getting at the same concept?
If we just lumped them all together, we could have a system with 4 meanarks: word, sacrament, prayer, discipline. Wouldn’t that be simpler?
[Update] Duh, I just noticed that WCF 25.4 gives a different “three marks” by which “particular Churches” may be judged “more or less pure”: word, sacrament, and “public worship performed more or less purely”. So between 1561 and 1646, what happened to the three marks?