Spinoza, Leibniz, Voltaire

It seems inarguable that Leibniz is a target of Voltaire's mockery in Candide. For, he explicitly challenges Leibniz' thesis that 'this is the best of all possible worlds' with factual examples of human suffering. But, his target is slightly inaccurate, for, it is, rather, another of Leibniz' principles to which those examples more immediately apply, one that is implicit in Spinoza's system, as well. What e. g. the Lisbon earthquake would more directly refute is, instead, the thesis of 'pre-established' harmony, which presumes to preclude the possibility of the existence of such dissonant events., as does Spinoza's Rationalism. And, since Spinoza rejects Leibniz' Best World thesis, because he argues that the thought of possible but non-actual worlds does not exist in the mind of God, it is, more precisely, the Harmony thesis that the existence of human suffering would refute. One fundamental problem for any Rational system is to explain the existence of conflict in a world presumably governed by a principle of non-contradiction, i. e. a world in which Harmony is guaranteed from the outset. Voltaire's expression of dissatisfaction with Leibniz' solution to that problem also applies to Spinoza's system.