The aim of this article is to elucidate Spinoza's conception of substance and mode by examinating Bayle's argument against Spinoza. Bayle criticizes Spinoza's substance monism and modification thesis on the basis of three argument, which include 'Argument from non-contradicton principle', 'Argument from incompatible parts', 'Argument from immutability'. However, Bayle's three arguments are not successful, since they are based on the misconception of Spinza's substance and mode, so they are out of focus. Furthermore, Bayle's issues can be ironed out by virtue of Curley's nomological interpretaion of substance and mode by which the relation between substance and mode can be interpreted as the relation between the most fundamental law and its instantiations. If follows from all these that Spinoza's conception of substance and mode is different from Descartes' and Aristotle's inherence-based conception of substance. But Several issues including the relation between substance and attributes, the comprehensive understanding of the mode system still remain puzzles in spite of the merits of nomological interpretation.