It is of great importance in a republic not only to guard the society against the oppression of its rulers, but to guard one part of the society against the injustice of the other part.
Different interests necessarily exist in different classes of citizens. If a majority be united by a common interest, the rights of the minority will be insecure. There are but two methods of providing against this evil: the one by creating a will in the community independent of the majority, that is, of the society itself; the other by comprehending in the society so many separate descriptions of citizens as will render an unjust combination of a majority of the whole very improbable, if not impracticable.
The first method prevails in all governments possessing a hereditary or self-appointed authority. This at best is but a precarious security; because a power independent of the society may as well espouse the unjust views of the major as the rightful interests of the minor party, and may possibly be turned against both parties.
The second method will be exemplified in the federal republic of the United States. While all authority in it will be derived from and dependent on the society, the society itself will be broken into so many parts, interests, and classes of citizens that the rights of individuals or of the minority will be in little danger from interested combinations of the majority.
In a free government the security for civil rights must be the same as that for religious rights. It consists in the one case in the multiplicity of interests, and in the other in the multiplicity of sects. The degree of security in both cases will depend on the number of interests and sects; and this may be presumed to depend on the extent of country and number of people comprehended under the same government.
This view of the subject must particularly recommend a proper federal system to all the sincere and considerate friends of republican government; since it shows that in exact proportion as the territory of the Union may be formed into more circumscribed confederacies, or States, oppressive combinations of a majority will be facilitated; the best security under republican forms, for the rights of every class of citizens, will be diminished; and, consequently, the stability and independence of some member of the government, the only other security, must be proportionally increased.
Justice is the end of government. It is the end of civil society. It ever has been and ever will be pursued until it be obtained or until liberty be lost in the pursuit. In a society, under the forms of which the stronger faction can readily unite and oppress the weaker, anarchy may as truly be said to reign, as in a state of nature, where the weaker individual is not secured against the violence of the stronger; and as in the latter state even the stronger individuals are prompted by the uncertainty of their condition to submit to a government which may protect the weak as well as themselves, so in the former state will the more powerful factions or parties be gradually induced by a like motive to wish for a government which will protect all parties, the weaker as well as the more powerful.
It can be little doubted that if the State of Rhode Island was separated from the confederacy, and left to itself, the insecurity of rights under the popular form of government within such narrow limits would be displayed by such reiterated oppressions of factious majorities that some power altogether independent of the people would soon be called for by the voice of the very factions whose misrule had proved the necessity of it.
In the extended republic of the United States, and among the great variety of interests, parties, and sects which it embraces, a coalition of a majority of the whole society could seldom take place on any other principles than those of justice and the general good; while there being thus less danger to a minor from the will of a major party, there must be less pretext, also, to provide for the security of the former, by introducing into the government a will not dependent on the latter; or, in other words, a will independent of the society itself.
It is no less certain than it is important, notwithstanding the contrary opinions which have been entertained, that the larger the society, provided it lie within a practical sphere, the more duly capable it will be of self-government. And happily for the republican cause, the practical sphere may be carried to a very great extent, by a judicious modification and mixture of the federal principle.
Source: James Madison, excerpt from Federalist Papers 51. Note, this is one paragraph in the original. Divided into paragraphs for easier reading.