German mathematician and philosopher Gottfried Leibniz had managed to delay his arrival in Hanover until the end of 1676, after making one more short journey to London, where he possibly was shown some of Newton's unpublished work on the calculus.

This fact was deemed evidence supporting the accusation, made decades later, that he had stolen the calculus from Newton.

On the journey from London to Hanover, Leibniz had stopped in The Hague where he had met Leeuwenhoek, the discoverer of microorganisms.

He had also spent several days in intense discussion with Spinoza, who had just completed his masterwork, the Ethics.

Leibniz respects Spinoza's powerful intellect, but is dismayed by his conclusions that contradict both Christian and Jewish orthodoxy.

Promoted in 1677, at his request, to Privy Counselor of Justice, a post he is to hold for the rest of his life, Leibniz is to serve three consecutive rulers of the House of Brunswick as historian, political adviser, and most consequentially, as librarian of the ducal library.

He henceforth employs his pen on all the various political, historical, and theological matters involving the House of Brunswick; the resulting documents form a valuable part of the historical record for the period.