But some one will say: at this point James makes an interjection. Having given an illustration, he now proceeds to argue his case, using the style of imaginary dialogue. He begins with an objection from another person. Here we face a problem in that the identity of this person is debated. There are three possible solutions, but none is totally convincing, and so we will have to settle for the least difficult.
(1) Some scholars take the person to be an ally of James interested in carrying on his argument further. He attacks the position of the “false” believer mentioned in verses 14-17. The strength of this interpretation is that it is consistent. The you always refers to the false believer, and I to James’ ally or James himself. However, there is a strong objection to this understanding, in that it has to interpret the adversative But differently, giving it a meaning which at best is rare and uncommon. It has to take the opening clause But some one will say as introducing a view similar to that of James. This makes it necessary to take But as “indeed” or “yes” (so American Standard Version). However, this is an exception, not its normal meaning; in fact the standard function of this particle is to introduce an objection, not an affirmation. In addition to this there is the question as to why James should introduce a third person here.
(2) Another possibility is to take the other person not as an ally but as an opponent of James. This will make it possible to translate the adversative as But introducing an objection, and the argument makes good sense. The problem comes as to where the objector’s words end and where those of James begin. Two solutions to this have been proposed. The first is to take the objector’s words as confined to the first three words in Greek, but in the form of a question: “Do you [James] have faith?” This is followed by James’ reply: “and I do have faith….” But this interpretation is a bit strained, because using “and I…” to introduce an answer is unnatural. A second solution is to take verses 18-19 as all from the objector, and James’ answer as beginning at verse 20. In this case, however, the objector appears to be supporting James’ view rather than contesting it, and it is therefore odd. In fact a more natural way to counter James’ view is to say something like: “You [James] have works; I [the objector] have faith.” To explain this difficulty it has been suggested that the original statement by the objector has somehow dropped out of the text, leaving only the reply by James. However, the great difficulty with this suggestion is that there is no manuscript evidence to support it.
(3) Another possibility is to take the pronouns “you” and “I” in the first part of the verse not as James and his opponent, but as two representative positions in the church. In this case the imaginary objector is simply pointing out that while some people have faith, others have deeds. He is claiming that faith and deeds may exist separately as different gifts (compare 1 Cor 12.4-10); a person may have one, but not necessarily both. James then is simply arguing against the separation of different gifts and saying that there cannot be any separation between faith and deeds. The function of the pronouns you and I is then equivalent to “one” and “another.” This is the understanding adopted by Good News Translation (“One person has faith, another has actions”) and Revised English Bible (“One chooses faith, another action”). In this case, in order to keep the sequence of the dialogue clear, it is desirable to add something not in the text to make the progression clear; for example, “My answer is” (Good News Translation), “To which I reply” (Revised English Bible), “I would answer” (Contemporary English Version), or “Then I will answer him” (Bible en français courant).

While not without its problems, interpretation (3) is perhaps the one to be adopted, as it appears to fit the context better and is the one favored by more translators and commentators.

James now makes a counter argument: Show me your faith apart from your works, and I by my works will show you my faith. Notice here a chiastic arrangement of “faith … works … works … faith.” Here Show me means “prove to me” (so New English Bible) or “demonstrate to me.” Barclay has brought out the spirit of the argument by rendering this as “I challenge you to prove to me.” The expression apart from, in the sense of “not accompanied by” (so New English Bible), argues that faith and action are inseparable. The imaginary opponent cannot possibly answer James’ challenge, as there is no way anyone can prove his or her faith without any action to support it.

An alternative translation model for this verse may be:
• Suppose someone disagrees and says, “One person believes in Christ, while another does kind deeds.” I would answer him, “You must prove to me that anyone can just believe in Christ without doing kind deeds. I on my part will show you that I believe in Christ, and so do kind deeds.”

Quoted with permission from Loh, I-Jin and Hatton, Howard A. A Handbook on The Letter from James. (UBS Handbook Series). New York: UBS, 1997. For this and other handbooks for translators see here .