Leibniz’s refutation of Cartesian dualism was based on the criticism of Descartes’ assumptions regarding the relationship between the mind and the body. Descartes claimed that the essence of the body was extension (Stumpf & Fieser, 2005, p. 233). According to Leibniz, to assume that such is the case would lead to the following problems: (1) it is not possible to posit a single substance that will serve as the foundational substance of all matter and (2) it is not possible to posit bodily objects as substances.
As an alternative to Descartes’ view, Leibniz conceived of an ontology whose foundational components are “simple substances” which he referred to as monads. The concept ‘monad’ is derived from the Greek term monas. Leibniz claimed that the term “signifies unity, or that which is one (hence)…simple substances, lives, souls, spirits are unified” (qtd Russel & Slater, 1992, p. 287). The manner in which such a conception may solve the problems specified above in Descartes’ metaphysics is elucidated by Leibniz in § 14 to §17 of the Monadology. § 14 to §17 contains Leibniz’s distinction between perception and apperception.
Perception refers to “the inner state of the monad representing external things” whereas apperception refers to “consciousness or reflective knowledge” of perception (Leibniz, 1992, p. 75). For Leibniz, perception is available in all things whereas apperception is limited to monads in rational creatures. In order to understand this, it is important to distinguish the three levels of monads: entelechies, souls, and spirits. Entelechies are the “created monads in general”, souls are the “ruling monads in animals” and spirits are the “ruling monads in rational creatures” (Leibniz, 1992, p.
78). Leibniz claims that although perception is available in all things, apperception is only available to souls or rational beings with consciousness, that being human beings. The reason for this is due to human beings’ capacity for consciousness which enables them to have a cognitive grasp of the world and hence all monads. As opposed to Descartes view regarding the body as an extension of the mind, Leibniz claims that the there is no distinction between both the body and the mind.
The reason for the assumed distinction is the assumption that experience affects consciousness or that human beings’ experience of the world affects and determines their view of the world. For Leibniz, such however is not the case, since all things are composed of the same substances and human beings’ capability to have knowledge of such substances is a result not of their experience of the individual monads themselves but from their ability to have cognitive grasp of such substances as a result of their rationality and consciousness.
References Hooker, M. (1992). Leibniz: Critical and Interpretive Essays. Np: Manchester U. P. Leibniz, G. (1992). G. W. Leibniz’s Monadology: An Edition for Students. Ed. Nicholas Rescher. London: Routledge. Russell, B. & J. Slater. (1992). The Philosophy of Leibniz: With an Appendix of Leading Passages. London: Routledge.