Galatians 3:1

"You foolish Galatians! Who has bewitched you? Before your very eyes Jesus Christ was clearly portrayed as crucified." NIV translation

Paul begins this section of his letter with what is seemingly a very harsh question. When he calls them "foolish", he is basically telling them that they have stopped using their mind (thinking). He goes on to describe them as "bewitched" and that speaks of the fact that they had listened to men who were causing them to forget what they had already learned and seen. Paul then reminds them that they were taught that Jesus Christ was crucified for their sins but these men had caused them to forget that.

Galatians 3:2

"I would like to learn just one thing from you: Did you receive the Spirit by observing the law or by believing what you heard?" NIV translation

Now, Paul asks them to remember their salvation experience. We are told throughout the Word that the presence of the Holy Spirit is evidence that the believer is saved. By asking this question of when they received the Spirit, he is asking them to think once again of that time when they were saved from the coming wrath of God. Did they get the Spirit because they kept the rules or because they believed that Jesus fulfilled the law for them?

Galatians 3:3

"Are you so foolish? After beginning with the Spirit, are you now trying to attain your goal by human effort?" NIV translation

Once again, Paul asks if they have stopped thinking and remembering their past experience with Christ. This foolishness is turning away from the Spirit and back to the law as a means of justification. That is foolish because the standard of the law is perfection and, as we know, we are imperfect people.