He was the author of a new theory of vision, of the celebrated 'new principle' of immaterialism, of a 'new argument' to prove the existence of God, of a bold criticism of the infinitesimal calculus
, of new proposals to improve the Irish economy, and of a novel panacea--tar-water --able to cure every disease in his diocese (where there were no doctors).
Leibniz was living in Paris and had just invented the infinitesimal calculus.
6) As this last remark indicates, the metaphysical outpourings of 1676 should in large part be understood as motivated by the antecedent success of the newly invented infinitesimal calculus, which had washed over Leibniz's metaphysics with the force of a tidal wave.
Despite Bernoulli being an accomplished practitioner of the infinitesimal calculus, it may perhaps be tempting to dismiss this as a quaint fallacy generated by an archaic understanding of the nature of the mathematical infinite.
In the "Letter to Varignon, with a Note on the `Justification of the Infinitesimal Calculus by That of Ordinary Algebra'" of 1702,(54) Leibniz's position is that we need not be committed to infinitesimals in any rigorous metaphysical sense.
Yet in doing so, he indicates just how weak a commitment to the infinite is required to work in the mathematical realm, even in the case of the infinitesimal calculus.