sult from the over-great preponderance of
any single element to the detriment of the others, the rational law lying
at the base of all varieties of political changes being that stability
can result only from the statical equilibrium produced by the
counteraction of opposing parts, since the more simple a constitution is
the more it is insecure. Plato had pointed out before how the extreme
liberty of a democracy always resulted in despotism, but Polybius
analyses the law and shows the scientific principles on which it rests.

The doctrine of the instability of pure constitutions forms an important
era in the philosophy of history. Its special applicability to the
politics of our own day has been illustrated in the rise of the great
Napoleon, when the French state had lost those divisions of caste and
prejudice, of landed aristocracy and moneyed interest, institutions in
which the vulgar see only barriers to Liberty but which are indeed the
only possible defences against the coming of that periodic Sirius of
politics, the [Greek]

There is a principle which Tocqueville never wearies of explaining, and
which has been subsumed by Mr. Herbert Spencer under that general law
common to all organic bodies which we call the Instability of the
Homogeneous. The various manifestations of this law, as shown in the
normal, regular revolutions and evolutions of the different forms of
government, {193a} are expounded with great clearness by Polybius, who
claimed for his theory in the Thucydidean spirit, that it is a [Greek],
not a mere [Greek], and that a knowledge of it will enable the impartial
observer {193b} to discover at any time what period of its constitutional
evolution any particular state has already reached and into what form it
will be next differentiated, though possibly the exact time of the
changes may be more or less uncertain. {193c}

Now in this necessarily incomplete account of the laws of political
revolutions as expounded by Polybius enough perhaps has been said to show
what is his true position in the rational development of the 'Idea' which
I have called the Philosophy of History, because it is the unifying of
history. Seen darkly as it is through the glass of religion in the pages
of Herodotus, more metaphysical than scientific with Thucydides, Plato
strove to seize it by the eagle-flight of speculation, to reach it with
the eager grasp of a soul impatient of those slower and surer inductive
methods which