The sole and proper witness of God

'God himself is the sole and proper witness of himself' (John Calvin, Institutes 1.11.1)

'He who we can know only through his own utterances is a fitting witness concerning himself' (Hilary of Poitiers, On the Trinity I, xviii)

I'm re-reading Calvin's Institutes this year. A little way in I'm thinking that I need to do some reflection on what I'm learning from it.

Perhaps the thing I'm most struck by so far is Calvin's determination to let God describe who God is. I am perhaps more aware of this because of reading a little Karl Barth recently, but it is great seeing that conviction that God is the proper witness of himself worked out in Calvin's explanation of what God is like.