Kant, Hume, and the Notion of Material Substance

In A Treatise of Human Nature, David Hume claims that the concept of substance, be it material or immaterial substance, is a fiction of the imagination. He maintains that we have no justification for positing the existence of substance. Instead, he argues the idea of substance is merely a fiction of the imagination; it is a confused idea that philosophers utilize in an attempt to explain aspects of the world that they do not understand. In his Critique of Pure Reason, Kant argues that certain concepts are necessary for our form of experience. He attempts to prove that the concept of material substance is one such concept. Kant claims that whenever we experience objects, we experience them temporally and maintains that our form of experience is necessarily temporal. Kant holds that temporal experience would not be possible without presupposing the concept of substance. This is because he believes that our notion of time necessarily assumes an underlying permanent. Kant dubs this permanent “substance.” Kant separates his proof of the necessity of the concept of material substance into two parts. In the First Analogy, he attempts to show that the concept of substance in general is necessary for our form of temporal experience. In the Refutation of Idealism, he attempts to show that the concept of material substance is a necessary concept. In this dissertation, I examine Kant’s proofs as they relate to Humean skepticism. I first consider what Hume means when he claims that the concept of material substance is merely a fiction of the imagination. Next, I examine Kant’s proofs in the First Analogy and the Refutation of Idealism. I argue that while the underlying assumptions Hume makes in the Treatise assume a Kantian notion of substance in general (i.e., Hume is unknowingly committed to the conclusion of the First Analogy), they do not commit him to Kant’s notion of material substance (i.e., Hume is not committed to the conclusion of the Refutation of Idealism).