No man of his time was more open-minded and free from prejudice than Fontenelle.

This quality of mind helped him to turn his eyes to the future.

Perrault and his predecessors were absorbed in the interest of the present and the past.
Descartes was too much engaged in his own original discoveries to do more than throw a passing glance at posterity.
Now the prospect of the future was one of the two elements which were still needed to fashion the theory of the progress of knowledge.

All the conditions for such a theory were present.

Bodin and Bacon, Descartes and the champions of the Moderns--the reaction against the Renaissance, and the startling discoveries of science--had prepared the way; progress was established for the past and present.