The seeds of Reformation doctrine in the Church fathers (HT: Scott Schultz), in the catholic definitions of the Trinity and the Incarnation. See? The earlier stuff matters, guys. A lot. As Doug Chaplin notes in discussing the second of the Thirty-Nine Articles of the Church of England,
There is, I think, something important in [the] concentrating on the Trinity before moving too quickly to the ordo salutis. The Son is defined by who he is in relationship to the Father before he is known in relationship to the human situation.
(Also a reason to talk about God before talking about Scripture in a confessional document in order to declare God’s lordship over epistemology, but I digress.)
If we’re to focus on God before man in our talk – as rightly we do unless God’s being himself is contingent on his creation – then this is crucial. After all, it’s the creeds that are recited in the Lord’s Day liturgy, not the Five Solas. Their articles of faith are more than propædeutics. Of course, the significance of the Trinity and the Incarnation takes more unpacking before we get from creedal affirmations to Reformation teachings, but it seems hard to argue with the premise that God himself – Holy God, Holy Mighty, Holy Immortal – is both the more essential teaching and the right place to start.
O Magnum Mysterium (sorry, I know it’s really a Christmas matins hymn):