Many changes and revolutions, he observes, may seem to have had most mischievous effects; yet every change has brought some advantage, for it has been a new experience and therefore has been instructive.
Man advances by committing errors.

The history of science shows (as Fontenelle had pointed out) that truth is reached over the ruins of false hypotheses.
The difficulty presented by periods of decadence and barbarism succeeding epochs of enlightenment is met by the assertion that in such dark times the world has not stood still; there has really been a progression which, though relatively inconspicuous, is not unimportant.
In the Middle Ages, which are the prominent case, there were improvements in mechanical arts, in commerce, in some of the habits of civil life, all of which helped to prepare the way for happier times.
Here Turgot's view of history is sharply opposed to Voltaire's.

He considers Christianity to have been a powerful agent of civilisation, not a hinderer or an enemy.

Had he executed his design, his work might well have furnished a notable makeweight to the view held by Voltaire, and afterwards more judicially developed by Gibbon, that "the triumph of barbarism and religion" was a calamity for the world.
Turgot also propounded two laws of development.

He observed that when a people is progressing, every step it takes causes an acceleration in the rate of progress.