There seems to be a close connection between verses 2 and 3, since the Greek has a transitional “for” (see Revised Standard Version) at the beginning of the latter verse, but the connection is not altogether clear. It may even be that Paul wants to remind his readers that often the sight of an erring brother (verse 1) creates in some a sense of spiritual superiority rather than a genuine desire to help. Or perhaps he is asserting the obvious fact that the proud man finds it difficult, if not impossible, either to lend a helping hand or to receive help of any kind. A third possibility is to connect verse 3 with verse 1, particularly the last part of that verse. There Paul was saying that a man should take care of himself in order not to be tempted. Here he continues to warn those who feel sure of themselves.
The word translated think is the same word used by Paul when talking of the three leaders of the Jerusalem church in 2.2,6,9. There the meaning is “to be regarded by others as important”; here the word is reflexive: “to regard oneself as important.”
When he really is nothing could be understood as a statement that describes believers in general, for since they owe their very lives to Christ, they have no right to claim importance or status of any kind. It is possible, however, that Paul has in mind those who think of themselves as important, and he is trying to show them how insignificant they really are.
The relation between the conditional clause if someone thinks he is something and the temporal clause when he really is nothing must be expressed in some languages as a conditional clause with an embedded relative clause, for example, “if someone, who really is nothing, thinks he is something.” However, to say merely that “he thinks he is something” may not carry any significance, for everyone is in a sense “something.” Therefore it may be necessary to say “if someone—and he really amounts to nothing at all—thinks he is something big,” or “… thinks he is very important.”
The verb translated deceiving is one which seems to have been coined by Paul himself; it cannot be found in earlier writings, and later it is used only by ecclesiastical writers. It is used only here in the New Testament, and a cognate noun (“deceiver”) occurs in Titus 1.10. Revised Standard Version, New American Bible, Phillips agree with Good News Translation in translating this verb as “deceive”; New English Bible, Knox have “delude.” He is only deceiving himself may be expressed in some languages as “he is only lying to himself,” or “it is just the same as though he were calling himself a fool.”
The relation between the three parts of this verse will depend on the exegetical viewpoint one takes. One way of rendering it would be “if a man thinks he is something, he is only fooling himself, for the truth is he is nothing.” Another way, representing another exegetical viewpoint, is “if a man thinks he is ‘somebody’, he is deceiving himself, for that very thought proves that he is nobody” (Phillips), or “it is the people who are not important who often make the mistake of thinking that they are” (Jerusalem Bible).
Quoted with permission from Arichea, Daniel C. and Nida, Eugene A. A Handbook on Paul’s Letter to the Galatians. (UBS Handbook Series). New York: UBS, 1976. For this and other handbooks for translators see here .