Gottfried Wilhelm Leibniz — "Everything that is possible demands to exist."

"The soul follows its own laws, and the body likewise follows its own laws; and they agree with each other in virtue of the pre-established harmony."

"Nothing is necessitated whose opposite is possible."

"If geometry were as much opposed to our passions and present interests as is ethics, we should contest it and violate it but little less, notwithstanding all the demonstrations of Euclid and Archimede…"

"All the different classes of beings which taken together make up the universe are, in the ideas of God who knows distinctly their essential gradations, only so many ordinates of a single curve so clos…"

"God alone is the primary unity, or the original simple substance, of which all created monads are products."