Please forgive the slightly tangential comment.

Voltaire's understanding of Leibniz is particularly inept. The facile optimism of Dr. Pangloss completely misses the mark.

Leibniz' uses the term "best of all possible worlds" in a somewhat technical sense, namely: the balancing of richness of phenomena with an elegant law structure (in physics). What is at issue is accordingly a very difficult maxima-minima problem.