But that advance would have been infinitely greater were it not that three general obstacles retarded it and even, at some times and in some countries, caused a retrogression.
These obstacles were wars, superstition, and the Jealousy of rulers who feared that progress in the science of politics would be dangerous to themselves.

In consequence of these impediments it was only in the time of Bodin and Bacon that the human race began to start anew from the point which it had reached in the days of Plato and Aristotle.
Since then the rate of progress has been accelerated, and this has been due to several causes.

The expansion of sea commerce has produced more wealth, and wealth means greater leisure, and more writers and readers.
In the second place, mathematics and physics are more studied in colleges, and their tendency is to liberate us from subjection to the authority of the ancients.

Again, the foundation of scientific Academies has given facilities both for communicating and for correcting new discoveries; the art of printing provides a means for diffusing them; and, finally, the habit of writing in the vulgar tongue makes them accessible.

The author might also have referred to the modern efforts to popularise science, in which his friend Fontenelle had been one of the leaders.
He proceeds, in this connection, to lay down a rather doubtful principle, that in any two countries the difference in enlightenment between the lowest classes will correspond to the difference between the most highly educated classes.