"1Paul, an apostle—not from men nor through man, but through Jesus Christ and God the Father, who raised him from the dead"
Galatians 1:1
It will be noticed in 6ff that Paul, in addressing himself to the Galatians, expresses surprise and dismay that they had been drawn away so quickly from the message he had preached to them. What was that message? We learn its content in Acts 13/14. Paul preached to them the life, death and resurrection of Christ, and forgiveness through His Name. He proclaimed the cross of Christ as the hope of the believer and the pattern of his life, and the anointing of the Spirit making that cross a life-transforming reality in ex- perience. This twofold emphasis on the cross and the Spirit is in one real sense also the theme of the Galatian epistle: the cross as the object of the believer's hope ('The Son of God loved me and gave Himself for me'), the principle of the believer's life ('I have been crucified with Christ'), and the Holy Spirit as the life and power of the believer ('Walk in the Spirit' and 'The fruit of the Spirit...'). Now, when the devil seeks to do a work in Christians' hearts to hinder or even destroy their faith, this is the twofold attack he makes: against the word of the cross on the one hand, and against the grace of the Holy Spirit on the other.
In their defection from the truth of the gospel the Galatians had been beguiled into doing two things: they were disputing the Apostle's message, and they were challenging his authority as an apostle. The false teachers had insinuated into their minds that there was a distinction between Paul's message and that of the other apostles, and suggesting by implication that his authority was therefore inferior to that of the other apostles. It is this that serves to explain the tremendous thrust of Paul's opening words in 1.