Tussen Newton en Wolff: het Rotterdams genootschap Verscheidenheid en Overeenstemming, 1760-1790

Between Newton and Wolff: the Rotterdam Society Diversity and Unanimity, 1760-1790 In this article, which is based on newly discovered source material, both published and in manuscript, I have attempted to sketch the relation between Newtonian and Leibniz-Wolffian philosophy within the context of a little known Rotterdam society of amateur scientists and scholars, called 'Diversity and Unanimity', founded in 1760. It seems that the founding members of this society, Adolf Hendrik Hagedoorn and Lieve Kaas, in their endeavour to promote an encyclopedic view of philosophical and scientific knowledge among the learned public of Rotterdam, set themselves two tasks. One was to keep Newtonianism both religious and pure, that is to say, free it from hypothetical and non-experimental elements that could be dangerous to religion. The other was to combine Newtonian physics, where necessary, with Leibniz-Wolffian metaphysics. They even went so far as to give Leibniz precedence over Newton in some questions of natural philosophy, such as the theories of light and the simple elements of material bodies. This seems quite remarkable, considering the great influence Newton exercised on physics in the Netherlands in the eighteenth century, but it can be explained from the first task they set themselves: they rejected those physical theories that could not be confirmed experimentally and were hostile to natural religion. Instead, they adopted Leibniz-Wolffian doctrines which in their view were more sound, not only scientifically, but also religiously and metaphysically.