Descartes’ primary objectives in Meditations were to argue for the existence of God and for the possibility of the soul’s immortality. In The Ethics, Spinoza intended that his arguments correct what he perceived as the main difficulties in Descartes’ philosophy – the potential paradox of infinite division of finite dimension, the conceptualization of God, the mind-body problem, and the question of free will.
It is worth first noting that Descartes and Spinoza held different views of God. For Descartes, God is both his creator and the creator of his supposedly innate idea of God. For Spinoza, God is not his creator, but instead equates to the totality of Nature. Spinoza views God/Nature’s essence as existence, and God/Nature as a single substance with two basic attributes – substance and thought. Spinoza proposes that God/Nature’s attributes generate an infinite number of existent or potentially existent components, including human minds and bodies.
Descartes expanded on the Cogito argument, “Thinking is another attribute of the soul; and here I discover what properly belongs to myself. This alone is inseparable from me. I am—I exist: this is certain.” Descartes claims that the essence of his individuality lies in his soul, his conscious mind, and not in his body, “I am not the assemblage of members called the human body.”
Descartes invested in two distortions for the sake of his argument–that ideas are more clear than sensations, and that the mind and body are distinct. Descartes identifies the pineal gland as the site of the inexplicable interaction between mind and body–he probably chose the pineal because it sits at the base of the brain.
Descartes’ mind-body dualism enabled him to claim both that God (author of Descartes’ innate idea of God) exists and that the soul persists after the death of the body. He claimed that mind and body could exist separately, but that the mind was tethered to the body during the body’s lifetime—convenient!
Spinoza responded to Cartesian mind-body dualism by countering that the mind knows of its own existence only through the body, “The human mind has no knowledge of the body, and does not know it to exist, save through the ideas of the modifications whereby the body is affected.” That is, the mind perceives the body through sensations that originate in the body. In essence, Spinoza is claiming that the mind perceives the body only through changes in the body, and we perceive external objects through their impacts upon our sensory organs – sight, sound, touch, taste, smell, and motion.
To Spinoza then, thought is simply a modification of the body. In a sense, he was sufficiently correct for a reawakening of interest in his ideas amongst those currently ‘meditating’ on how the brain constructs consciousness through its physiological processes. (Neurologist Antonio Damasio is author of Looking for Spinoza: Joy, Sorrow, and the Feeling Brain)Other : Princess Elisabeth and the Problem of Mind-Body Interaction .