Christians should know that social justice internet mobs are a far cry from truly Biblical justice that accords with God's law. But we don't. Biblical justice requires multiple witnesses, matching stories, and objective facts considered by an appropriate authority. A Justice Primer is written by two longtime pastors who have worked inside denominations, sessions, and institutions, and who have seen more than their share of controversy where people do not know what the rules are. A whispered conversation is not authoritative. An anonymous comment on a blog is not authoritative. A party of disgruntled church members who "feel abused" is not authoritative. Instead, the key to true justice is due process conducted by wise men who know how to weigh evidence. God is justice, and it is because of His justice that Jesus went to the cross. Therefore, we must care about what justice is and how God says to pursue it.