But, in writing history, by what means are we to arrive at truth? By following the rules of logic. Let us first take for granted that a great effect is always due to a great cause, never to a small one; in other words, an accident, insignificant in appearance, never leads to important results without a pre-existing cause, which has permitted this slight accident to produce a great effect. The spark only lights up a vast conflagration when it falls upon combustible matters previously collected. Montesquieu thus confirms this idea: “It is not fortune,” he says, “which rules the world.... There are general causes, whether moral or physical, which act in every monarchy, raising, maintaining, or overthrowing it; all accidents are subject to these causes, and if the fortune of a battle--that is to say, a particular cause--has ruined a state, there was a general cause which made it necessary that that state should perish through a single battle: in a word, the principal cause drags with it all the particular accidents.”[1] If during nearly a thousand years the Romans always came triumphant out of the severest trials and greatest perils, it is because there existed a general cause which made them always superior to their enemies, and which did not permit partial defeats and misfortunes to entail the fall of the empire. If the Romans, after giving an example to the world of a people constituting itself and growing great by liberty, seemed, after Cæsar, to throw themselves blindly into slavery, it is because there existed a general reason which by fatality prevented the Republic from returning to the purity of its ancient institutions; it is because the new wants and interests of a society in labour required other means to satisfy them. Just as logic demonstrates that the reason of important events is imperious, in like manner we must recognise in the long duration of an institution the proof of its goodness, and in the incontestable influence of a man upon his age the proof of his genius. The task, then, consists in seeking the vital element which constituted the strength of the institution, as the predominant idea which caused man to act. In following this rule, we shall avoid the errors of those historians who gather facts transmitted by preceding ages, without properly arranging them according to their philosophical importance; thus glorifying that which merits blame, and leaving in the shade that which calls for the light. It is not a minute analysis of the Roman organisation which will enable us to understand the duration of so great an empire, but the profound examination of the spirit of its institutions; no more is it the detailed recital of the most trivial actions of a superior man which will reveal the secret of his ascendency, but the attentive investigation of the elevated motives of his conduct.