The literary context comprises evidence from within the epistle of James itself. It is worth enumerating the various aspects of this context.
We are dealing with writing that is certainly more didactic than narrative, but we can qualify this classification in two respects. First, the instruction makes frequent reference to the readers' historical circumstances ("scattered among the nations . . . you face trials of many kinds . . . fights and quarrels among you"), showing the writer to be consciously addressing particular events and situations. The historical narrative behind the writing of the letter will therefore be relevant. Second, the instruction displays a definite rhetorical flavor. Second-person address is prevalent throughout the letter. That James would employ the second person rhetorically toward people not actually receiving the letter is most clearly confirmed in 5:1-6. Both Mayor and Adamson, while wanting to allow for some possible address of professing Christians even in this vehement passage, do admit that 5:1-6 seems to be referring primarily to unbelievers (Mayor 1897:148; Adamson 1976:183-84). Adamson even compares it quite appropriately to Churchill's wartime speeches, which were formally directed at the enemy but intended to encourage his own people.
Understanding adelphos in 1:9 to be the referent for both tapeinos in 1:9 and plousios in 1:10 does seem to be a natural way to read these verses. The important caution in using this argument of "natural" reading is that it may simply be making the ancient text fit with what seems natural to our modern ears. The difference between the ancient text and our modern thinking is precisely the gap we are trying to cross. The fact is that the grammar in 1:9-10 does not require this reading of adelphos as a common referent. Another very possible way to read the passage would be to see ho adelphos ho tapeinos standing together as a unit and ho plousios as the contrasting subject, with adelphos not repeated because the rich here are not "brothers," and with kauchastho the verb for both subjects.
The writer of the epistle typically employs contrasts in successive clauses, sentences or groups of sentences. Examples are found within 1:19, 2:5 and 4:7-8. This stylistic device is used at times to make emphatic contrast between the "rich" and "brothers," as in 2:5-6 and 5:1, 7.
There is a frequent use of diverse similes and metaphors, as in the hunting and fishing imagery of 1:14 followed immediately by the childbearing imagery in 1:15. This manner of description is definitely applied to the rich in 1:10-11 (with the wild flower image) and in 5:1-6 (with the images of destruction) for vivid emphasis. This use of imagery is part of the pattern of strong, intense language throughout the letter. Douglas Moo captures the tone of James's letter as "profound moral earnestness" (Moo 1985:9). In the case of 5:1-6, Adamson describes James's writing as "sarcastic," "dramatic" and "forceful" (Adamson 1976:183).
Whenever James speaks of the rich as plousios there is a consistently negative message without any hope offered. In 1:10-11, the rich will pass away like a wild flower. In 2:6-7, the rich are seen as persecuting Christians and slandering the name of Christ. In 5:1-6, the rich are guilty of greed, injustice, self-indulgence and murder. They are promised only misery. The only other use of plousios, in 2:5, is not a contradiction to this rule, since plousios is used here in its figurative sense: those who are poor in material wealth are said to be "rich in faith." The fact that James's other descriptions of people with wealth (in 2:2 and 4:13) do not employ the term plousios does leave the term with a uniformly negative connotation in this letter. This, of course, is the heart of the case made by Davids and others in viewing "the rich" in 1:10 as non-Christians. Their argument is quite plausible and consistent with the entirety of James's message.
The narratives authors employ can reveal intended meaning that may be unclear from their didactic statements alone. James's narratives about the rich and the poor become additional evidence of his meaning.
 1:2. The prevalent situation of James's readers is the suffering of diverse trials. Though this does not mention poverty explicitly, the "humble circumstances" in 1:9 seem to be brought up as a prime example of the trials.
 1:27. The example chosen to illustrate pure religion is action on behalf of needy people.
 2:2-4. Rich people may attend a Christian meeting, but they are not to be shown favoritism above the poor.
 2:6-7. The rich typically exploit Christians and blaspheme the name of Christ.
 2:15. The example of proper deeds accompanying genuine faith is to help a "brother or sister" who is poor.
 4:13-17. Those who have any money are warned to know their complete dependence on the Lord.
 5:1-6. The rich are seen as people who arrogantly abuse the power that their wealth brings.
The picture derived from this narrative material in the letter is that James wrote with a particularly intense concern for the poor, and that this was probably because his Christian readers were predominantly poor or at least suffering some significant economic hardship. There would have been exceptions--some rich people would be turning to Christ, and these would have been the referents of 2:2 (Davids 1982:108). However, in general adelphos and tapeinos became almost synonymous.
Adamson dismisses the view that the rich of 1:10 are non-Christians as having "little to commend it" (1976:61). He lists the weaknesses of that view as being that it is unnatural not to supply the term brother to complete rich in this context, that it requires an excessively ironical sense for 1:10 and that it makes the verse only loosely connected to the context of trials begun in 1:2. These arguments now appear rather surprising since, on the contrary, so far the view that the rich are unbelievers seems to be very possible from the syntax, quite appropriate to James's intense, imaginative, rhetorical style of writing and thoroughly in keeping with the historical context of Christians suffering trials.
Gathering together the connotations with which James uses the term, we can say that the discourse meaning of plousios is one who has material wealth and typically displays arrogance in abusing its power.