WRITER, The apostle Paul. 
DATE. Probably between 55 and 60 A.D.
TO WHOM ADDRESSED. To the churches in Galatia, a district in Asia Minor, the exact boundaries of which are uncertain.
MAIN THEMES. A Defense of the Doctrine of Justification by Faith, warnings against Reversion to Judaism and a Vindication of Paul's Apostleship.
THE MAGNA CHARTA OF THE CHURCH. This epistle has been so called by some writers. The main argument is in favour of Christian liberty in opposition to the teachings of the Judaizers. These false teachers insisted that the observance of the ceremonial law was an essential part of the plan of salvation.
KEY TEXT
Ga 5:1
KEY CHAIN showing the current of thought
Ga 1:6 2:11-16 3:1-11 4:9-11 5:1-7 6:15
EMPHATIC WORDS. "Faith," "Grace," "Liberty," "The Cross"
THE EPISTLE MAY BE DIVIDED INTO FOUR PARTS
PART I. The salutation and introduction
Ga 1:1-9
PART II. A narrative of Paul's experiences in support of his claim to true apostleship.
(1) The gospel which he preached came directly by revelation from Christ, while he himself was a zealous Jew persecuting the church
Ga 1:10-16
(2) For years he was away from the church at Jerusalem and laboured independently of the other apostles
Ga 1:17-23
(3) He was under divine direction in his work among the Gentiles, and in the case of Titus, the Greek, had insisted that he should be free from the observance of the ceremonial law
Ga 2:1-5
(4) The church at Jerusalem indorsed his apostleship, and work among the Gentiles
Ga 2:7-10
(5) He had not hesitated to rebuke Peter, Barnabas and other Christian Jews, when he saw that they were yielding to ritualistic tendencies
Ga 2:11-14
PART III. Paul's Defence of the Doctrine of Justification by Faith apart from the Works of the Law.
(1) By showing the folly of Christian Jews abandoning their new faith and light, and returning to the old legalism
Ga 2:15-21
(2) By appealing to the former spiritual experience of the Galatians
Ga 3:1-5
(3) By showing that Abraham was justified by faith
Ga 3:6-9
(4) By showing that the law had no redeeming power, but brought a curse upon the disobedient, from which Christ redeemed believers
Ga 3:10-14
(5) By proving that the law could not disannul the covenant of salvation by faith
Ga 3:15-18
(6) By indicating the purpose of the law as a schoolmaster to prepare the way for Christ
Ga 3:19-25
(7) By showing the losses of those who surrender their faith in Christ, and relapse into legalism.
(a) They lose the blessing of their inheritance as children of God, and return to the bondage of ceremonialism
Ga 3:26 - 4:11
(b) They have lost the sense of appreciation for labours performed in their behalf
Ga 4:11-16
(c) They are in danger of becoming the children of Abraham after the flesh, instead of the children of promise
Ga 4:19-31
(d) They not only lose their spiritual liberty, but make Christ's sacrifice of no avail for them
Ga 5:1-6
PART IV. Warnings, Instructions, and Exhortations.
(1) Warnings in regard to false teachers, and the misuse of liberty
Ga 5:7-13
(2) Exhortations concerning the spiritual life.
(a) The conflict between the flesh and Spirit
Ga 5:17,18
(b) The works of the flesh which exclude from the kingdom of God
Ga 5:19-21
(c) The fruits of the Spirit which should be manifest in Christian life
Ga 5:22-26
(3) The characteristics of the spiritual life.
(a) Charitableness, and burden bearing
Ga 6:1,2
(b) Humility, self-examination, self-reliance and benevolence
Ga 6:3-6
(c) The law of sowing and reaping holds good in the moral realm
Ga 6:7-9
(4) The contrast between the doctrine of the false teachers and that of Paul. The former, glory in ceremonial rites and the marks in the flesh; the latter, in the cross, and the marks of the Lord Jesus
Ga 6:12-17
(Outline from Thompson’s Chain Reference Bible)