Why must our gospel come primarily from Paul's writings?
Our gospel must come primarily from Paul's writings because Paul did not receive his Gospel from Christ's earthly ministry or the Twelve. He had private seminary training with the ascended Lord after crucifixion, resurrection, and ascension. From that, he sets forth the doctrines of grace, revealing things given by the Lord now seated at the Father's right hand.
Les explains that Paul was adamant he did not receive his Gospel from the earthly ministry of Christ. He did not go back down to Jerusalem to check in with the Twelve; instead, he had his own private seminary training with the Ascended Lord from heaven out in the desert. When he came away, he began the doctrines of grace. Les maintains that our Gospel has to come primarily from the writings of this Apostle because Paul is revealing things revealed to him from the Lord after His crucifixion, resurrection, and ascension, from where He is now seated at the Father's right hand. Les also connects this to moving beyond the elementary principles of Christ, using the analogy of advancing in mathematics after learning basic arithmetic.