Abstract

In this paper, I argue for a novel reading of Spinoza’s position in his exchange with Boyle about Boyle’s experiment with nitre. Boyle claimed to have shown through experiments that nitre ceased to be nitre after heating. Spinoza disagreed and proposed the alternative hypothesis that nitre has changed its state and not its nature. Spinoza’s position was construed in the literature as rational scepticism denying that experiments can yield knowledge of essences because all sensory experience is underdetermined and open to multiple interpretations. I argue for an alternative reading of Spinoza’s position which focuses on Bacon’s notion of crucial instance. According to this reading, Spinoza did not deny the possibility of knowing by experimentation whether nitre has changed its nature, he asked for a crucial instance, i.e. an experiment that would refute the hypothesis that nitre has changed merely its state. Spinoza’s argumentative strategy shows that, contrary to the mainstream reading, the representational content of sensory ideas can be determined even if it does not represent the essence of the object: we can know with absolute, rather than merely moral, certainty whether nitre ceased to be nitre without knowing what nitre is.