Here, however, it may seem that we are transgressing the limit which divides Ethics from Politics: for Ethics is primarily concerned with the rules which ought to govern the private conduct of individuals; and it is commonly thought that private persons ought to obey even laws that they regard as unjust, if established by lawful authority. Still, this is doubted in the case of laws that seem extremely unjust: as (_e.g._) the Fugitive Slave law in the United States before the rebellion. At any rate it seems desirable that we should here digress somewhat into political discussion; partly in order to elucidate the notion of Justice, which seems to be essentially the same in both regions, and partly because it is of great practical importance to individuals, in regulating private conduct beyond the range of Law-observance, to know whether the laws and established order of the society in which they live are just or unjust.
Now perhaps the most obvious and commonly recognised characteristic of just laws is that they are Equal: and in some departments of legislation, at least, the common notion of Justice seems to be exhaustively expressed by that of Equality. It is commonly thought, for example, that a system of taxation would be perfectly just if it imposed exactly equal burdens upon all:[206] and though this notion of ‘equal burden’ is itself somewhat difficult to define with the precision required for practical application, still we may say that Justice here is thought to resolve itself into a kind of equality. However, we cannot affirm generally that all laws ought to affect all persons equally, for this would leave no place for any laws allotting special privileges and burdens to special classes of the community; but we do not think all such laws necessarily unjust: _e.g._ we think it not unjust that only persons appointed in a certain way should share in legislation, and that men should be forced to fight for their country but not women. Hence some have said that the only sense in which justice requires a law to be equal is that its execution must affect equally all the individuals belonging to any of the classes specified in the law. And no doubt this rule excludes a very real kind of injustice: it is of the highest importance that judges and administrators should never be persuaded by money or otherwise to show ‘respect of persons.’ So much equality, however, is involved in the very notion of a law, if it be couched in general terms: and it is plain that laws may be equally executed and yet unjust: for example, we should consider a law unjust which compelled only red-haired men to serve in the army, even though it were applied with the strictest impartiality to all red-haired men. We must therefore conclude, that, in laying down the law no less than in carrying it out, all inequality[207] affecting the interests of individuals which appears arbitrary, and for which no sufficient reason can be given, is held to be unjust. But we have still to ask, what kind of reasons for inequality Justice admits and from what general principle (or principles) all such reasons are to be deduced?