Herodotus, while believing on principle in the supernatural, yet was sceptical at times. Thucydides simply ignored the supernatural. He did not discuss it, but he annihilated it by explaining history without it. Polybius enters at length into the whole question and explains its origin and the method of treating it. Herodotus would have believed in Scipio's dream. Thucydides would have ignored it entirely. Polybius explains it. He is the culmination of the rational progression of Dialectic. 'Nothing,' he says, 'shows a foolish mind more than the attempt to account for any phenomena on the principle of chance or supernatural intervention. History is a search for rational causes, and there is nothing in the world - even those phenomena which seem to us the most remote from law and improbable - which is not the logical and inevitable result of certain rational antecedents.'
Some things, of course, are to be rejected A PRIORI without entering into the subject: 'As regards such miracles,' he says, (15) 'as that on a certain statue of Artemis rain or snow never falls though the statue stands in the open air, or that those who enter God's shrine in Arcadia lose their natural shadows, I cannot really be expected to argue upon the subject. For these things are not only utterly improbable but absolutely impossible.'
'For us to argue reasonably on an acknowledged absurdity is as vain a task as trying to catch water in a sieve; it is really to admit the possibility of the supernatural, which is the very point at issue.'
What Polybius felt was that to admit the possibility of a miracle is to annihilate the possibility of history: for just as scientific and chemical experiments would be either impossible or useless if exposed to the chance of continued interference on the part of some foreign body, so the laws and principles which govern history, the causes of phenomena, the evolution of progress, the whole science, in a word, of man's dealings with his own race and with nature, will remain a sealed book to him who admits the possibility of extra-natural interference.
The stories of miracles, then, are to be rejected on A PRIORIrational grounds, but in the case of events which we know to have happened the scientific historian will not rest till he has discovered their natural causes which, for instance, in the case of the wonderful rise of the Roman Empire - the most marvellous thing, Polybius says, which God ever brought about (16) - are to be found in the excellence of their constitution ([Greek text which cannot be reproduced]), the wisdom of their advisers, their splendid military arrangements, and their superstition ([Greek text which cannot be reproduced]). For while Polybius regarded the revealed religion as, of course, objective reality of truth, (17) he laid great stress on its moral subjective influence, going, in one passage on the subject, even so far as almost to excuse the introduction of the supernatural in very small quantities into history on account of the extremely good effect it would have on pious people.
But perhaps there is no passage in the whole of ancient and modern history which breathes such a manly and splendid spirit of rationalism as one preserved to us in the Vatican - strange resting-place for it! - in which he treats of the terrible decay of population which had fallen on his native land in his own day, and which by the general orthodox public was regarded as a special judgment of God sending childlessness on women as a punishment for the sins of the people. For it was a disaster quite without parallel in the history of the land, and entirely unforeseen by any of its political-economy writers who, on the contrary, were always anticipating that danger would arise from an excess of population overrunning its means of subsistence, and becoming unmanageable through its size. Polybius, however, will have nothing to do with either priest or worker of miracles in this matter. He will not even seek that 'sacred Heart of Greece,' Delphi, Apollo's shrine, whose inspiration even Thucydides admitted and before whose wisdom Socrates bowed. How foolish, he says, were the man who on this matter would pray to God. We must search for the rational causes, and the causes are seen to be clear, and the method of prevention also. He then proceeds to notice how all this arose from the general reluctance to marriage and to bearing the expense of educating a large family which resulted from the carelessness and avarice of the men of his day, and he explains on entirely rational principles the whole of this apparently supernatural judgment.
Now, it is to be borne in mind that while his rejection of miracles as violation of inviolable laws is entirely A PRIORI - for discussion of such a matter is, of course, impossible for a rational thinker - yet his rejection of supernatural intervention rests entirely on the scientific grounds of the necessity of looking for natural causes. And he is quite logical in maintaining his position on these principles. For, where it is either difficult or impossible to assign any rational cause for phenomena, or to discover their laws, he acquiesces reluctantly in the alternative of admitting some extra-natural interference which his essentially scientific method of treating the matter has logically forced on him, approving, for instance, of prayers for rain, on the express ground that the laws of meteorology had not yet been ascertained. He would, of course, have been the first to welcome our modern discoveries in the matter. The passage in question is in every way one of the most interesting in his whole work, not, of course, as signifying any inclination on his part to acquiesce in the supernatural, but because it shows how essentially logical and rational his method of argument was, and how candid and fair his mind.