But the question of method, to which I am compelled always to return, is not yet exhausted. There is another aspect in which it may be regarded, and I shall now proceed to treat of it.
One of the greatest difficulties with which the modern historian has to contend is the enormous complexity of the facts which come under his notice: D'Alembert's suggestion that at the end of every century a selection of facts should be made and the rest burned (if it was really intended seriously) could not, of course, be entertained for a moment. A problem loses all its value when it becomes simplified, and the world would be all the poorer if the Sibyl of History burned her volumes. Besides, as Gibbon pointed out, 'a Montesquieu will detect in the most insignificant fact relations which the vulgar overlook.'
Nor can the scientific investigator of history isolate the particular elements, which he desires to examine, from disturbing and extraneous causes, as the experimental chemist can do (though sometimes, as in the case of lunatic asylums and prisons, he is enabled to observe phenomena in a certain degree of isolation). So he is compelled either to use the deductive mode of arguing from general laws or to employ the method of abstraction, which gives a fictitious isolation to phenomena never so isolated in actual existence. And this is exactly what Polybius has done as well as Thucydides. For, as has been well remarked, there is in the works of these two writers a certain plastic unity of type and motive;whatever they write is penetrated through and through with a specific quality, a singleness and concentration of purpose, which we may contrast with the more comprehensive width as manifested not merely in the modern mind, but also in Herodotus. Thucydides, regarding society as influenced entirely by political motives, took no account of forces of a different nature, and consequently his results, like those of most modern political economists, have to be modified largely (20) before they come to correspond with what we know was the actual state of fact. Similarly, Polybius will deal only with those forces which tended to bring the civilised world under the dominion of Rome (ix. 1), and in the Thucydidean spirit points out the want of picturesqueness and romance in his pages which is the result of the abstract method ([Greek text which cannot be reproduced]) being careful also to tell us that his rejection of all other forces is essentially deliberate and the result of a preconceived theory and by no means due to carelessness of any kind.
Now, of the general value of the abstract method and the legality of its employment in the sphere of history, this is perhaps not the suitable occasion for any discussion. It is, however, in all ways worthy of note that Polybius is not merely conscious of, but dwells with particular weight on, the fact which is usually urged as the strongest objection to the employment of the abstract method - Imean the conception of a society as a sort of human organism whose parts are indissolubly connected with one another and all affected when one member is in any way agitated. This conception of the organic nature of society appears first in Plato and Aristotle, who apply it to cities. Polybius, as his wont is, expands it to be a general characteristic of all history. It is an idea of the very highest importance, especially to a man like Polybius whose thoughts are continually turned towards the essential unity of history and the impossibility of isolation.
Farther, as regards the particular method of investigating that group of phenomena obtained for him by the abstract method, he will adopt, he tells us, neither the purely deductive nor the purely inductive mode but the union of both. In other words, he formally adopts that method of analysis upon the importance of which I have dwelt before.
And lastly, while, without doubt, enormous simplicity in the elements under consideration is the result of the employment of the abstract method, even within the limit thus obtained a certain selection must be made, and a selection involves a theory. For the facts of life cannot be tabulated with as great an ease as the colours of birds and insects can be tabulated. Now, Polybius points out that those phenomena particularly are to be dwelt on which may serve as a [Greek text which cannot be reproduced] or sample, and show the character of the tendencies of the age as clearly as 'a single drop from a full cask will be enough to disclose the nature of the whole contents.' This recognition of the importance of single facts, not in themselves but because of the spirit they represent, is extremely scientific; for we know that from the single bone, or tooth even, the anatomist can recreate entirely the skeleton of the primeval horse, and the botanist tell the character of the flora and fauna of a district from a single specimen.
Regarding truth as 'the most divine thing in Nature,' the very 'eye and light of history without which it moves a blind thing,'
Polybius spared no pains in the acquisition of historical materials or in the study of the sciences of politics and war, which he considered were so essential to the training of the scientific historian, and the labour he took is mirrored in the many ways in which he criticises other authorities.