Evangelism. The Great Commission is so important which is why people get upset when it's done differently or wrongly or not according to what the Bible teaches. Sovereignty of God. Arguably the greatest of all the great doctrines. And people do argue about it, what it means and how it changes our lives. Put Evangelism and Sovereignty of God together and it's like the fusion of two atoms. You get a tremendous release of energy that can either power up or destroy your faith.