I thought the answer was simple and obvious. It is neither application nor wonder but the Holy Spirit who changes us.
Every preacher has stories of people being changed in a way that appears a miracle given the sermon. The conversion of one of Adrian’s favourites – Spurgeon – is surely a good example.
I can do nothing by myself.
Big NB: I am in no way suggesting or supporting a lack of preparation, nor am I ignoring the time in prayer and the work of the Spirit during preparation and delivery. I am saying the effectiveness of anything I do as a Christian is not my works but that of the Holy Spirit working through me in a miraculous way.
NB2: Nor am I decrying the need for wonder and application as well as relevance, engagement, orthodoxy etc. But the work in a persons heart is not my work but God’s