s the study of physiology should precede the study of
pathology, just as the laws of disease are best discovered by the
phenomena presented in health, so the method of arriving at all great
social and political truths is by the investigation of those cases where
development has been normal, rational and undisturbed.

The critical canon that the more a people has been interfered with, the
more difficult it becomes to generalise the laws of its progress and to
analyse the separate forces of its civilisation, is one the validity of
which is now generally recognised by those who pretend to a scientific
treatment of all history: and while we have seen that Aristotle
anticipated it in a general formula, to Polybius belongs the honour of
being the first to apply it explicitly in the sphere of history.

I have shown how to this great scientific historian the motive of his
work was essentially the search for causes; and true to his analytical
spirit he is careful to examine what a cause really is and in what part
of the antecedents of any consequent it is to be looked for. To give an
illustration: As regards the origin of the war with Perseus, some
assigned as causes the expulsion of Abrupolis by Perseus, the expedition
of the latter to Delphi, the plot against Eumenes and the seizure of the
ambassadors in Boeotia; of these incidents the two former, Polybius
points out, were merely the pretexts, the two latter merely the occasions
of the war. The war was really a legacy left to Perseus by his father,
who was determined to fight it out with Rome. {205}

Here as elsewhere he is not originating any new idea. Thucydides had
pointed out the difference between the real and the alleged cause, and
the Aristotelian dictum about revolutions, [Greek], draws the distinction
between cause and occasion with the brilliancy of an epigram. But the
explicit and rational investigation of the difference between [Greek] and
[Greek] was reserved for Polybius. No canon of historical criticism can
be said to be of more real value than that involved in this distinction,
and the overlooking of it has filled our histories with the contemptible
accounts of the intrigues of courtiers and of kings and the petty
plottings of backstairs influence--particulars interesting, no doubt, to
those who would ascribe the Reformation to Anne Boleyn's pretty face, the
Persian war to the influence of a doctor or a curtain-lecture from
Atossa, or the French Revolutio