Dualism consists of a set of philosophical positions about the relationship between mind and matter (or body). The dualism began with the assertion that mental phenomena are, in some respects, other than physical. One of the earliest known formulations of the dualistic conception of the mind-body relation was proposed by the Samkhya and Yoga schools of Indian philosophy atstika (circa -650), and divided the world into Purusha (spiritual substance) and Prakriti. (material substance). More specifically, Yogasūtra de Patañjali offers an analytical approach to the nature of the mind.
The first appearances of dualistic ideas in Western philosophy occur in the works of Plato and Aristotle. Each of them considered, for different reasons, that intelligence as a faculty of the mind or soul could not be identified with or explained in physical terms. The most famous conception of dualism, however, comes from René Descartes, who argues that the mind is a non-physical and non-extended substance, a res cogitans (thinking substance). Descartes was the first to clearly identify the mind with consciousness and self-perception, and to distinguish it from the brain, seat of intelligence; as a result of which he was the first to formulate the mind-body problem in its present form.
The most common argument used to justify dualism is the common sense that conscious experience is distinct from inanimate matter. When asked about the nature of the mind, an average person usually responds by identifying him with his self, his personality, his soul, or a similar entity. It almost always refuses to consider that the mind is simply assimilable to the brain, finding the idea of the existence of a single ontological entity too mechanistic, or even completely unintelligible. Many philosophers of the mind today consider that such intuitions are misleading, and that they should be examined in light of the critical faculties and empirical evidence provided by science to determine whether their foundation is real. The visibly different, if not irreconcilable, properties of the mind and the physical constitute another strong argument in favor of dualism. Mental events are purely subjective, physical events are not. If one can reasonably ask someone how one feels after a burn on the finger, what a blue sky looks like or how pleasant music sounds, it is however insane or at least strange about the sensations provided by a increased release of glutamate in the dorsolateral region of the hippocampus.
Philosophers of the mind call the subjective qualities of mental events “qualia” or “raw sensations“. This makes a particular effect of feeling pain, of seeing a shade of familiar blue, and so on. The qualia involved in such mental events seems hardly reducible to any physical substance. If consciousness (the mind) can exist independently of physical reality (the brain), it is necessary to explain how physical memories can come to consciousness. Dualism must therefore explain how consciousness affects physical reality. One of the explanations, proposed by Arnold Geulincx and Nicolas Malebranche, requires a direct intervention of God in all the interactions between the body and the spirit. Albert Einstein’s position is similar to him, in that the scientist considers that the mental faculty of understanding sensory impressions is miraculous. Another possible explanation has been proposed by C. S. Lewis, in the form of the argument arising from reason: if, as monism wants, the totality of thoughts are only the effects of physical causes, the reason could be explained by such causes. But to explain reason by material causes constitutes a petition of principle by presupposing reason. Therefore, monism self-refutes it.
The zombie argument is based on a thought experiment developed by Todd Moody, and developed by David Chalmers in his book The Conscious Mind. The idea is that one can imagine a body, and therefore conceive the existence of a body, devoid of any conscious state. The argument of Chalmers consists in the fact that it seems plausible that such a being can exist, since all that the possibility of this existence requires is the validity in this being of all the characteristics of a zombie as described by the physical sciences, and only they. Since none of the concepts treated by physics refer to consciousness or other mental phenomena, and by definition any physical entity can be described scientifically by physics, the distance between conceivability and the possibility of existence of the zombie is not very big. Others like Daniel Dennett reply that a philosophical zombie is an incoherent or implausible concept. It has also been suggested that, by virtue of physicalism, everyone must believe that everyone, including himself, can be a zombie, or that no one can be – this being the assertion that one’s own belief that everyone to be or not to be a zombie is a product of the physical world, and therefore this belief is no different from anyone else’s. This argument was expressed by Dennett as follows: “Zombies think to be conscious, to have qualia, to suffer from pain; they are simply “false” (according to this deplorable tradition), in a way that neither they nor we could discover!“
Interactionist dualism, or more simply interactionism, is a particular form of dualism that Descartes was the first to espouse in his Meditations. In the twentieth century, it was mainly defended by Karl Popper and John Carew Eccles. Interactionist dualism is the view that mental states, such as beliefs or desires, interact causally with physical states. Descartes’ most famous argument in favor of interactionism can be summarized as follows: Seth has a clear and distinct idea of his mind as a thinking substance that is not spatially extended (ie that can not be measured in terms of length, width, height, etc.). He also has a clear and distinct idea of his body as a spatially extended substance, subject to a possible quantification, and incapable of the least thought; from which it follows that the mind and the body are not identical in their radically different properties. At the same time, however, it is clear that Seth’s mental states (desires, beliefs, etc.) have causal effects on his body and vice versa.