Montesquieu sought to show that the vicissitudes of societies were subject to law; Voltaire believed that events were determined by chance where they were not consciously guided by human reason.

The element of chance is conspicuous even in legislation: "almost all laws have been instituted to meet passing needs, like remedies applied fortuitously, which have cured one patient and kill others." On Voltaire's theory, the development of humanity might at any moment have been diverted into a different course; but whatever course it took the nature of human reason would have ensured a progress in civilisation.

Yet the reader of the Essay and Louis XIV.

might well have come away with a feeling that the security of Progress is frail and precarious.

If fortune has governed events, if the rise and fall of empires, the succession of religions, the revolutions of states, and most of the great crises of history were decided by accidents, is there any cogent ground for believing that human reason, the principle to which Voltaire attributes the advance of civilisation, will prevail in the long run?
Civilisation has been organised here and there, now and then, up to a certain point; there have been eras of rapid progress, but how can we be sure that these are not episodes, themselves also fortuitous?
For growth has been followed by decay, progress by regress; can it be said that history, authorises the conclusion that reason will ever gain such an ascendancy that the play of chance will no longer be able to thwart her will?
Is such a conclusion more than a hope, unsanctioned by the data of past experience, merely one of the characteristics of the age of illumination?
Voltaire and Montesquieu thus raised fundamental questions of great moment for the doctrine of Progress, questions which belong to what was soon to be known as the Philosophy of History, a name invented by Voltaire, though hardly meant by him in the sense which it afterwards assumed.
3.
Six years before Voltaire's Essay was published in its complete form a young man was planning a work on the same subject.