Gottfried Wilhelm Leibniz / 1646–1716 / Leipzig, Electorate of Saxony, Holy Roman Empire (now Germany) / Philosopher, Mathematician, Historian
It is unworthy of excellent men to lose hours like slaves in the labor of calculation which could safely be relegated to anyone else if machines were used.Source: Machina arithmetica in qua non addito[sic] tantum et subtractio sed multiplicatio nullo, divisio vero pæne nullo animi labore peragantur [An arithmetical machine in which not only addition and subtraction, but also multiplication and division, may be carried out with almost no mental labor], unpublished manuscript, 1685 (on the hand-cranked calculating machine he invented in 1673).
If you could blow the brain up to the size of a mill and walk about inside, you would not find consciousness.Source: Monadology, 1714; section 17.
God has chosen the best of all possible worlds.Source: Theodicy, 1695; section 168 et passim.
Interconnectedness of All Things
Now this connexion or adaptation of all created things to each and of each to all, means that each simple substance has relations which express all the others, and, consequently, that it is a perpetual living mirror of the universe.Source: Monadology, 1714; section 56.
Principle of Sufficient Reason
Nihil est sine ratione.
[There is nothing without a reason.]Source: Theory of Abstract Motion: Fundamental Principles, 1671; section 24 (earliest of many references to the “Principle of Sufficient Reason” throughout his work).