Having now examined Polybius's attitude towards the supernatural and the general ideas which guided his research, I will proceed to examine the method he pursued in his scientific investigation of the complex phenomena of life. For, as I have said before in the course of this essay, what is important in all great writers is not so much the results they arrive at as the methods they pursue. The increased knowledge of facts may alter any conclusion in history as in physical science, and the canons of speculative historical credibility must be acknowledged to appeal rather to that subjective attitude of mind which we call the historic sense than to any formulated objective rules. But a scientific method is a gain for all time, and the true if not the only progress of historical criticism consists in the improvement of the instruments of research.
Now first, as regards his conception of history, I have already pointed out that it was to him essentially a search for causes, a problem to be solved, not a picture to be painted, a scientific investigation into laws and tendencies, not a mere romantic account of startling incident and wondrous adventure. Thucydides, in the opening of his great work, had sounded the first note of the scientific conception of history. 'The absence of romance in my pages,' he says, 'will, I fear, detract somewhat from its value, but I have written my work not to be the exploit of a passing hour but as the possession of all time.' (18) Polybius follows with words almost entirely similar. If, he says, we banish from history the consideration of causes, methods and motives ([Greek text which cannot be reproduced]), and refuse to consider how far the result of anything is its rational consequent, what is left is a mere [Greek text which cannot be reproduced], not a [Greek text which cannot be reproduced], an oratorical essay which may give pleasure for the moment, but which is entirely without any scientific value for the explanation of the future. Elsewhere he says that 'history robbed of the exposition of its causes and laws is a profitless thing, though it may allure a fool.' And all through his history the same point is put forward and exemplified in every fashion.
So far for the conception of history. Now for the groundwork. As regards the character of the phenomena to be selected by the scientific investigator, Aristotle had laid down the general formula that nature should be studied in her normal manifestations.
Polybius, true to his character of applying explicitly the principles implicit in the work of others, follows out the doctrine of Aristotle, and lays particular stress on the rational and undisturbed character of the development of the Roman constitution as affording special facilities for the discovery of the laws of its progress. Political revolutions result from causes either external or internal. The former are mere disturbing forces which lie outside the sphere of scientific calculation. It is the latter which are important for the establishing of principles and the elucidation of the sequences of rational evolution.
He thus may be said to have anticipated one of the most important truths of the modern methods of investigation: I mean that principle which lays down that just as 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. (19)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 text which cannot be reproduced], draws the distinction between cause and occasion with the brilliancy of an epigram. But the explicit and rational investigation of the difference between [Greek text which cannot be reproduced], and [Greek text which cannot be reproduced] 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 Revolution to Madame de Maintenon, but without any value for those who aim at any scientific treatment of history.