Like modern-day Masons, the first century had its own mystery religions. Coded greetings, secret handshakes, covert initiations are part and parcel of such societies. Such secrecy creates curiosity which—if exploited successfully—leads to increased membership.
It really was not the image of Diana in her temple which attracted adherents. The allure of possibly becoming a member of a secret, mysterious society was much greater. Membership in such a guild (especially if you were a silversmith) could produce a prosperous income (Acts 19:24-25).
Such clandestine shenanigans cannot compare in any way with the mystery at the heart and soul of the temple which Jesus built. Though unknown to the sons of men in bygone ages (Ephesians 3:5), history’s greatest mystery—the salvation of all humanity in Christ through the gospel (Ephesians 3:6)—is not known through a secret handshake or coded password. Instead, it has been revealed by the Holy Spirit to the holy apostles and prophets (Ephesians 3:5) so that all nations can live in obedience to the faith (Romans 16:26).
History’s greatest mystery is the gospel of spiritual victory in Christ. Now that it has been revealed, it is to be preached to every creature (Mark 16:15) in all nations (Matthew 28:19). It is history’s greatest mystery because of its message, its scope, and its offer.
Great is Jesus of Nazareth!