There may be something in Comte's suggestion that he could not give his conception any real consistency or vigour, just because he was himself unconsciously under the influence of excessive faith in the effects of legislative action.
A fundamental defect in Montesquieu's treatment of social phenomena is that he abstracted them from their relations in time.

It was his merit to attempt to explain the correlation of laws and institutions with historical circumstances, but he did not distinguish or connect stages of civilisation.

He was inclined to confound, as Sorel has observed, all periods and constitutions.

Whatever be the value of the idea of Progress, we may agree with Comte that, if Montesquieu had grasped it, he would have produced a more striking work.

His book announces a revolution in the study of political science, but in many ways belongs itself to the pre-Montesquieu era.
2.
In the same years in which Montesquieu was busy on the composition of the Esprit des lois, Voltaire was writing his Age of Louis XIV.