6. "To guarantee to every State in the Union a republican form of
government; to protect each of them against invasion; and on application
of the legislature, or of the executive (when the legislature cannot be
convened), against domestic violence."

In a confederacy founded on republican principles, and composed of
republican members, the superintending government ought clearly
to possess authority to defend the system against aristocratic or
monarchial innovations. The more intimate the nature of such a union may
be, the greater interest have the members in the political institutions
of each other; and the greater right to insist that the forms
of government under which the compact was entered into should be
SUBSTANTIALLY maintained. But a right implies a remedy; and where
else could the remedy be deposited, than where it is deposited by the
Constitution? Governments of dissimilar principles and forms have been
found less adapted to a federal coalition of any sort, than those of
a kindred nature. "As the confederate republic of Germany," says
Montesquieu, "consists of free cities and petty states, subject to
different princes, experience shows us that it is more imperfect than
that of Holland and Switzerland." "Greece was undone," he adds, "as soon
as the king of Macedon obtained a seat among the Amphictyons." In
the latter case, no doubt, the disproportionate force, as well as the
monarchical form, of the new confederate, had its share of influence on
the events. It may possibly be asked, what need there could be of such
a precaution, and whether it may not become a pretext for alterations in
the State governments, without the concurrence of the States themselves.
These questions admit of ready answers. If the interposition of the
general government should not be needed, the provision for such an event
will be a harmless superfluity only in the Constitution. But who can say
what experiments may be produced by the caprice of particular States, by
the ambition of enterprising leaders, or by the intrigues and influence
of foreign powers? To the second question it may be answered, that if
the general government should interpose by virtue of this constitutional
authority, it will be, of course, bound to pursue the authority. But the
authority extends no further than to a GUARANTY of a republican form of
government, which supposes a pre-existing government of the form which
is to be guaranteed. As long, therefore, as th