The state of the Galatians, while heathen, was similar but worse. They had not been heirs in a state of temporary slavery, but frankly slaves to the mere element-spirits, those undivine gods they worshipped. If they now Judaize, they return to the same slavery. To make the imperfect OT Law an ultimate religious authority is to prefer nature-worship to Christ. Subordinate spirits, however over-ruled by God, instituted the Law. Here Paul comes nearer his great Gnostic follower Marcion than anywhere else; but, while Marcion hated the OT, Paul rejects only the Law, and rejects it only if it becomes a rival to the Gospel. His thought is delicately balanced on a knife-edge. In Rom., emphasis on the ceremonial (not part but aspect of the) Law disappears; it is viewed on its moral side as the law of God. In a later epistle, Col., the ceremonial again predominates.
Galatians 4:9. rather to be known of God: note the feeling of mystery, and cf. 1 Corinthians 8:1 ff.
Galatians 4:11. I am afraid: he does not despair of winning back his readers.