The distinction between natural necessity and metaphysical necessity is examined. An account is advanced of the logical form of statements of natural law, contrasting with that of D. M. Armstrong. The relationship between law-statements and counterfactual conditionals is discussed. The claim of scientific essentialists that natural laws are metaphysically necessary is challenged as resting on a questionable account of the identity conditions of properties. It is argued that Saul Kripke’s model of a posteriori knowledge of necessary truths does not enable us to understand how knowledge of natural laws is possible on the scientific essentialist view of them.
Keywords: D. M. Armstrong, counterfactual conditionals, Ellis, Saul Kripke, laws of nature, metaphysical necessity, natural necessity, properties, scientific essentialism