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.’ {76} Polybius follows with words almost entirely similar. If, he says, we banish from history the consideration of causes, methods and motives (_τὸ διὰ τί_, _καὶ πως_, _καὶ τίνος χάριν_), and refuse to consider how far the result of anything is its rational consequent, what is left is a mere _ἀγώνισμα_, not a _μάθημα_, 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.