The part which it played in Bossuet is usurped by those general causes which he had learned from Montesquieu.
But his systematic mind would have organised and classified the ideas which Montesquieu left somewhat confused.

He criticised the inductions drawn in the Esprit des lois concerning the influence of climate as hasty and exaggerated; and he pointed out that the physical causes can only produce their effects by acting on "the hidden principles which contribute to form our mind and character." It follows that the psychical or moral causes are the first element to consider, and it is a fault of method to try to evaluate physical causes till we have exhausted the moral, and are certain that the phenomena cannot be explained by these alone.

In other words, the study of the development of societies must be based on psychology; and for Turgot, as for all his progressive contemporaries, psychology meant the philosophy of Locke.
General necessary causes, therefore, which we should rather call conditions, have determined the course of history--the nature of man, his passions, and his reason, in the first place; and in the second, his environment,--geography and climate.

But its course is a strict sequence of particular causes and effects, "which bind the state of the world (at a given moment) to all those which have preceded it." Turgot does not discuss the question of free-will, but his causal continuity does not exclude "the free action of great men." He conceives universal history as the progress of the human race advancing as an immense whole steadily, though slowly, through alternating periods of calm and disturbance towards greater perfection.

The various units of the entire mass do not move with equal steps, because nature is not impartial with her gifts.