Substance has been a concept of investigation in the history of philosophy until Antiquity. This concept suggesting something that lies beneath the things and that is the ground for all things, has been explained as certain types of being which provide basis for all phenomena. Apart from the various arguments about the concept of substance put forward by many philosophers in the history of philosophy, the arguments proposed by Spinoza and Leibniz about the concept sit at the heart of their metaphysics. On one hand, Spinoza argued that there is only one substance which is God, while on the other hand, Leibniz asserted that substance is monad. The present study aims to explore the concept of substance as discussed in the metaphysics of Spinoza and Leibniz and the problems evoked by their conceptualisations.
Key Words: Spinoza, Leibniz, Substance, Metaphysics