This is Part 2 of a four (or five) part series based on a conference-length version of a longer paper I’m currently preparing for submission to academic journals. Part 1 is just a brief introduction to the paper, but it has generated a deep and ongoing conversation about the nature of justice which is well worth reading (and joining). You can also consult the full paper at any time.
This section of the paper is more substantial, but it is also primarily exegetical. I’m certainly interested in hearing critiques or additions to my interpretations of Rawls and Hume. But we can also continue some of the deeper discussion about justice if some readers would like to critique substantive elements of Hume and/or Rawls as interpreted. Another question that might be worth exploring in light of our discussion of Part 1: how similar or different is this account of the circumstances of justice from the account(s) we find in Plato’s Republic?
II. The ‘Circumstances of Justice’ in Hume and Rawls
Hume’s account first appears in the Treatise of Human Nature, where he identifies justice as an artificial virtue, grounded in social conventions. These conventions arise in response to the natural mismatch between individual human needs and abilities – an inadequacy that can only be alleviated by joining together with others. And yet this need for others only gives rise to considerations of justice when combined with further facts about the qualities of the human mind (“selfishness” and “limited generosity”) and about the situation of the external objects upon which we rely (“easy change” and “scarcity”).
Justice finds its origins in the conventions that arise to address these basic human needs. Where there is no need for such conventions, there will be no justice on this account. But also, as Hume emphasizes when reprising these points in the second Enquiry, justice cannot arise where such conventions are inadequate for those needs. Extremes of either “abundance” or “necessity” would make justice useless, as would either “perfect moderation and humanity” or “perfect rapaciousness and malice.” Finally, Hume adds a condition of ‘rough equality’ to the list of circumstances necessary for justice to apply, since justice would again prove useless with respect to those who have no power of resistance or reprisal. 
Drawing on Hume’s initial distinction between “the situation of external objects” and “qualities of the human mind,” Rawls divides his own account of the circumstances of justice into “objective” and “subjective” conditions. According to Rawls, the objective circumstances of justice are (numbering mine):
(1)[M]any individuals coexist together at the same time on a definite geographic territory. (2) These individuals are roughly similar in physical and mental powers; or at any rate, their capacities are comparable in that no one among them can dominate the rest. (3) They are vulnerable to attack, (4) and all are subject to having their plans blocked by the united force of others. (5) Finally, there is the condition of moderate scarcity…
And the subjective circumstances are (numbering mine):
(6)[W]hile the parties have roughly similar needs and interests, or needs and interests in various ways complimentary, so that mutually advantageous cooperation among them is possible, (7) they nevertheless have their own plans of life. These plans, or conceptions of the good, lead them to have different ends and purposes, and to make conflicting claims on the natural and social resources available. Moreover, although the interests advanced by these plans are not assumed to be interests in the self, they are interests of a self that regards its conception of the good as worthy of recognition and that advances claims in its behalf as deserving satisfaction. (8) I also suppose that men suffer from various shortcomings of knowledge, thought, and judgment. Their knowledge is necessarily incomplete, their powers of reasoning, memory, and attention are always limited, and their judgment is likely to be distorted by anxiety, bias, and a preoccupation with their own affairs. Some of these defects spring from moral faults, from selfishness and negligence; but to a large degree, they are simply part of men’s natural situation. As a consequence individuals not only have different plans of life but (9) there exists a diversity of philosophical and religious belief, and of political and social doctrines.
It is easy enough to see why Rawls credits Hume as his source when we look at the objective conditions. Conditions 2 and 5 appear explicitly in Hume’s account. Condition 3 is covered under Hume’s condition of ‘easy change,’ which in its initial elaboration includes a concern with the violent dispossession of the fruits of one’s labor and of one’s good fortune. However, condition 4’s more general concern with one’s “plans” already represents a move away from Hume’s focus on basic human needs. Finally, on the simplest reading, Condition 1 is simply a precondition for the operation of the other listed conditions, since, e.g. we are only vulnerable to attack when others are physically close enough to execute such an attack.
The implausibility of Rawls’s claim to have added “nothing essential” to Hume’s list becomes clearer when we examine the subjective conditions. Condition 6 is easy enough to connect to Hume’s account, given the role of sympathy in his account of moral motivation, and given his contention that motives of perfect malice would render justice useless. But in specifying Condition 7, Rawls explicitly rejects a tendency toward selfishness as a pre-condition for the circumstances of justice. To be sure, Hume’s own account of selfishness is more nuanced than the term might suggest. He recognizes that we don’t care only about ourselves, but he insists that we care most about ourselves, followed by our close friends and relations, with mere acquaintances and strangers coming in last. Nonetheless, the core of Hume’s account makes no appeal to different conceptions of the good. The only issue is to what extent we prefer our own good, and that of our close relations, over the good of others – not what disputes we might have over which things are indeed good.
Conditions 8 and 9 are similarly absent from Hume’s account. He does make allowances for a general tendency to choose our short-term good over our long-term good in explaining the need for government to enforce the rules of justice. But this falls far short of the range of limits canvased under Condition 7, limits Rawls would later group under the label “the burdens of judgment.” And Hume shows no interest in having the rules of justice accommodate this kind of philosophical disagreement, as we can see from his impatience with moral appeals based on religion.
Rawls’s protestations to the contrary, it shouldn’t be surprising that his account differs dramatically from Hume’s. First, Hume views justice primarily as a system of rules assigning property rights. Second, Hume’s account of the circumstances of justice is, in the first instance, an exercise in speculative anthropology. In the conclusion of Book 3 of the Treatise, Hume describes his discussion of justice and the other virtues as analogous to the work of an anatomist. And in both the Treatise and the Enquiry he is concerned with the “origins” of justice – that is, under what conditions do rules of justice actually arise in human societies. This is not to say that there is no normative element in Hume’s treatment of justice – after all, he categorizes justice as an artificial virtue. And, given his view of moral psychology, there can be obligations of justice only if there is some deeper human motive served by justice. Thus, for Hume, showing the anthropological origins of justice is a precondition for establishing its normative bona fides.
Rawls, in contrast, is concerned primarily with the normative project of identifying and defending the correct principles of justice. For Rawls, these are not, in the first instance, the circumstances under which we find people appealing to justice. Rather they are the circumstances to which the concept of justice applies. And because Rawls’s theory of moral psychology is more Kantian than Humean, he does not assume that normative concepts can apply only where they are useful or where they satisfy other non-moral motives.
Nonetheless, Rawls is able to incorporate much from Hume’s account because of his view of society as a cooperative scheme for mutual advantage and of justice as the virtue governing the distribution of those advantages. Justice only applies when there are social advantages to be distributed, and there will typically be such advantages only when society is useful, in Hume’s sense. Taken together then, this Rawlsian/Humean view represents the traditional account of the circumstances of justice.
 Treatise 184.108.40.206-3 [Book#.Part#.Section#.Paragraph#]
 Treatise 220.127.116.11
 Hume, Enquiry Concerning the Principles of Morals, 3.1.12 [Section#.Part#.Paragraph#]
 Enquiry 3.1.18
 Rawls 1999, p. 110
 Rawls 1999, p. 110
 Treatise 18.104.22.168 It is noteworthy that this concern doesn’t reappear in the Enquiry. This may be due to the specific scope of the argument there, which only requires an illustration of justice’s dependence on circumstance.
 But talk of a “definite geographic territory” suggests something a bit more heavy duty, e.g. relating to Rawls’s treatment of justice for a closed society. I don’t explore that complication here.
 Treatise 22.214.171.124 and 126.96.36.199
 See Treatise sections 3.2.6 and 3.2.7
 Rawls 1993, p. 54-8 and 2001, p. 35-7
 Enquiry 9.3
 This is evident from the central role possession and property play in Hume’s account. See, e.g. Enquiry 3.8 where he counts opening granaries in an emergency as a suspension of justice, rather than an exercise of it.
 Hubin (1979) interprets Hume as engaged in a descriptive/historical characterization of the circumstances of justice in the Treatise but as engaged in a more normative treatment of the subject in the second Enquiry. (See his p. 5). I find Hume’s appeal to the ‘utility’ of justice in the Enquiry to be ambiguous between these two readings. But either way, as Hubin points out, Rawls also rejects a normative account of justice that grounds it in utility in this way.
 Treatise 188.8.131.52; however, see Krause 2008, p. 225, note 52 for a reminder not to take this passage to mean Hume has no moral aims in the Treatise.
 See, e.g. Treatise 184.108.40.206 and Enquiry 3.12
 Thanks to Sharon Krause for this point.
 Treatise 220.127.116.11 “that no action can be virtuous, or morally good, unless there be in human nature some motive to produce it, distinct from the sense of its morality”
Hubin, D. Clayton. 1979. “The Scope of Justice.” Philosophy & Public Affairs 9(1):3-24.
Hume, David. 1998. An Enquiry Concerning the Principles of Morals. Edited by Tom L. Beauchamp. Oxford: Oxford University Press.
Hume, David. 2000. A Treatise of Human Nature. Edited by David Fate Norton and Mary J. Norton. Oxford: Oxford University Press.
Krause, Sharon. 2008. Civil Passions. Princeton, NJ: Princeton University Press.
Rawls, John. 1993. Political Liberalism. Cambridge, MA: Harvard University Press.
Rawls, John. 1999. A Theory of Justice, rev. ed. Cambridge, MA: Harvard University Press.
Rawls, John. 2001. Justice as Fairness: A Restatement. Edited by Erin Kelly. Cambridge, MA: Harvard University Press.