How can we logically persuade others that scriptures like the Gita are the words of God?

From: Rashmi Kanojia Bakker

People don’t believe that the scriptures are words of the Supreme Lord. They always say its written by men (specially Bhagavad Gita), that is why they doubt its authenticity. What should be the best way to logically make them understand that scriptures are truly the words of Lord and have come down through a bonafide disciplic succession?