Aristotle explores other aspects of corruption as well. Consistent with classical Greek sensitivities, Aristotle did not hold commerce in high regard. He believed that in a healthy constitution all commercial transactions would be rigorously subject to the moral purposes of community (both household and polis). That means that economic activity should be directed toward the ends of communal life. Economic transactions aimed at mere profit are signs of a community in which self-interest prevails over public interest. A corrupt society, then, is one in which gain is valued over friendship and fellow-feeling, where private interests are set above the common good. When materialism drives the people, both individually and collectively, leading them to focus solely on their own personal gains and losses whenever they make public decisions, corruption has set in and civic virtue has been driven out.
Good citizens think, speak, deliberate, decide, and act with an eye to the common good. The focus of the good Aristotelian (or republican) citizen rests on the betterment of the community, on the general welfare as opposed to their merely personal benefit. If I choose a specific policy on the basis of its effects on my own bank account, I am to that extent failing in virtue; I am to that extent a poor citizen. If I vote for a particular candidate because he or she espouses policies that would serve my own personal ends (such as being able to pay lower taxes so I can gratify more material desires), I am to that extent lacking in civic virtue; I am to that extent acting in a corrupt manner. If I refuse to participate in political affairs because I think they are silly or not worth the time away from my own business or leisure, I am acting selfishly, placing my private interests ahead of those of the community. A community that contains many of these sorts of citizens -- citizens who generally place self-interest ahead of public interest -- is rife with corruption. A political order in which officials or candidates for office cater to the selfish interests of their constituents through base appeals rather than raising them above their private benefit to a concern for the public good is a diseased, even degenerate, political order.
It is important to be clear about what exactly this commitment to the common good entails. Most of those working in what has come to be called the republican tradition (I speak here of a tradition of political thought, not a political party) -- including in addition to Aristotle, Machiavelli, Harrington, Montesquieu, and Rousseau -- have looked for ways to imbue citizens with a devotion to the common good while recognizing that human societies (like human beings) degenerate and decay over time. In short, these writers treated the citizen obsessed with the common good as a standard against which to judge actually existing societies, and concluded that real political worlds could never live up to the standard. Some who have not read these writers deeply miss this point: the notion that real people can never be withdrawn so effectively from their personal interests and their personal ties that they become focused in all things on the public interest.
One thing for which the American founders are routinely praised is their realism. They understood that most people most of the time cannot be counted upon to rise above their personal interests. Republican idealism found its way into the writings of the so-called anti-federalists, who opposed the Constitution because it created a big, distant government, making corruption inevitable (this was a lesson they had drawn from republican political theory as well as from history). The federalists responded by noting that most people are preoccupied with their own personal affairs and cannot be expected to set those concerns aside routinely to look for and act upon the common good. James Madison, writing in the Federalist Papers was particularly clear about this, repeatedly proposing a setting of interest against interest and noting that not even elite public leaders can be expected to be angels. Madison insisted on "auxiliary precautions" to help ensure that the common good would sometimes be pursued by government, precautions in the form of an expanded sphere (a strong national government as opposed to a weak confederacy or a "dismemberment" of the nation into separate states) and structural devices (branches of government with limited powers, two houses in Congress, a system of federalism pitting states against the national government, and so forth). In short, in Madison's view, the goal of institutional design is to approximate a political world in which the common good is sought by all, especially by government; but this approximation requires multiple structures, limits, and processes that had the effect of filtering out self-interest so that the common interest remained.
Once we take into consideration the realistic understanding that few (if any) citizens are likely to be so caught up with the common good that they generally subordinate their personal to the public interest, the meaning of corruption (at least in this regard) shifts. On a Madisonian view, individuals cannot be considered corrupt simply because they do not obsess about the common good. Rather, corruption becomes a systemic matter, a characteristic of a political order that fails to work in such a way as to foster the public interest by setting ambition against ambition, self-interest against self-interest -- a political order that fails to generate leaders capable of setting aside their own interests and the interests of their friends in order to seek the good of all. Corruption is a disease of the commonwealth rather than a sin committed by individuals.
Here we can return to Aristotle's distaste for commerce. Madison and the other federalists (following David Hume in this) did not share this distaste, for they saw commerce as crucial for the public benefit despite (or perhaps because of) its roots in self-interest. Indeed, while Charles Beard may have gone too far in claiming that the Constitution was designed specifically to protect the interests of the wealthy mercantile class emerging in the new nation, it is true that many of America's leaders in the late eighteenth and early nineteenth centuries (and in the years since, of course) believed that there was virtue in commerce, or at least that it was only when government protects a vibrant commerce that anything like the common good can be achieved.
But, at least until the end of the eighteenth century, those of the Madisonian persuasion regarding commerce were balanced by those, particularly among the anti-federalists, who persisted in the view, written deep in the republican tradition, that in order to ensure civic virtue and guard against corruption it was essential to keep the citizens poor or at least not permit them to become rich. Even Jefferson was ambivalent about commerce: on the one hand, he recognized the importance of commerce to the well-being of the new nation; on the other hand, he disdained the kind of commerce emerging in the big eastern cities with its bankers and endless trading designed to make money rather than meet needs. These traditionalists held that great riches were a sign of corruption and that commerce tended to focus everyone's attention on pecuniary gain rather than the public good. They held up the person of "the middling sort" as a model of republican virtue. Such a person was neither too poor nor too rich, but was as comfortable behind a plow as he was in the public forum deciding matters of political import. (One need think only of the equation of George Washington with Cincinnatus to see this point.) Only a person not too caught up in commercial affairs, not too rich (that is, not filthy rich), not too focused on personal gain, can be a good citizen. At least at crucial moments, a citizen must be able to set aside private interests in the pursuit of the common good. Those whose attention is too centered on trade, the accumulation of wealth, the proliferation of material good for themselves and those close to them, make poor citizens. In fact, they tend to corrupt the body politic because everything they do is aimed at personal benefit no matter what the ultimate cost to the health of the community.