What does it mean to begin in the Spirit?
Beginning in the Spirit means starting the Christian life by Paul's Gospel through faith plus nothing, not by works of the Law. It is the newness of spirit rather than the oldness of the letter, and it contrasts with trying to grow deeper through fleshly legalism.
Les explains that having begun in the Spirit is defined in Galatians 3:3 as beginning by Paul's Gospel through faith plus nothing. The believer has been delivered from the Law, which was an administration of death, and now serves in newness of spirit, not in the oldness of the letter. The contrast is trying to move into a deeper spiritual life by the flesh, which in the Galatian churches meant legalism and Law. Les notes that it is part of the old Adamic nature to want to be under some kind of Law, but the spiritual realm comes by believing the Gospel.
Are ye so foolish? having begun in the Spirit, are ye now made perfect by the flesh?