Spinoza: Common Notions and Laws of Nature

In this paper, I argue for a novel reading of Spinoza’s position in his exchangewith Boyle about Boyle’s experiment with nitre. Boyle claimed to have shownthrough experiments that nitre ceased to be nitre after heating. Spinozadisagreed and proposed the alternative hypothesis that nitre has changed itsstate and not its nature. Spinoza’s position was construed in the literature asrational scepticism denying that experiments can yield knowledge ofessences because all sensory experience is underdetermined and open tomultiple interpretations. I argue for an alternative (...) reading of Spinoza’sposition which focuses on Bacon’s notion of crucial instance. According tothis reading, Spinoza did not deny the possibility of knowing byexperimentation whether nitre has changed its nature, he asked for a crucialinstance, i.e. an experiment that would refute the hypothesis that nitre haschanged merely its state. Spinoza’s argumentative strategy shows that,contrary to the mainstream reading, the representational content of sensoryideas can be determined even if it does not represent the essence of theobject: we can know with absolute, rather than merely moral, certaintywhether nitre ceased to be nitre without knowing what nitre is. (shrink)

In this paper, through a close reading of Spinoza's use of common notions I argue for the role of experiential and experimental knowledge in Spinoza's epistemology.

Spinoza scholars have claimed that we are faced with a dilemma: either Spinoza's definitions in his Ethics are real, in spite of indications to the contrary, or the definitions are nominal and the propositions derived from them are false. I argue that Spinoza did not recognize the distinction between real and nominal definitions. Rather, Spinoza classified definitions according to whether they require a priori or a posteriori justification, which is a classification distinct from either the real/nominal or the intensional/extensional classification. (...) I argue that Spinoza uses both a priori and a posteriori definitions in the Ethics and that recognizing both types of definitions allows us to understand Spinoza's geometric method in a new way. We can now understand the geometric method as two methods, one resulting in propositions that Spinoza considers to be absolutely certain and another resulting in propositions that Spinoza does not consider certain. The latter method makes use of a posteriori definitions and postulates, whereas the former method uses only a priori definitions and axioms. (shrink)