Human consciousness is itself a huge complex of memes (or more exactly, meme-effects in brains) that can best be understood as the operation of a “von Neumannesque” virtual machine implemented in the parallel architecture of a brain that was not designed for any such activities. The powers of this virtual machine vastly enhance the underlying powers of the organic hardware on which it runs, but at the same time many of its most curious features, and especially its limitations, can be explained as the byproducts of the kludges that make possible this curious but effective reuse of an existing organ for novel purposes. [Daniel C. Dennett, Consciousness Explained (New York, NY: Black Ray Books, 1991), p. 21]
There is no single, definitive “stream of consciousness,” because there is no central Headquarters, no Cartesian Theater where “it all comes together” for the perusal of a Central Meaner. Instead of such a single stream (however wide), there are multiple channels in which specialist circuits try, in parallel pandemoniums, [/253] to do their various things, creating Multiple Drafts as they go. Most of these fragmentary drafts of “narrative” play short-lived roles in the modulation of current activity but some get promoted to further functional roles, in swift succession, by the activity off a virtual machine in the brain. The seriality of this machine (its “von Neumannesque” character) is not a “hard-wired” design feature, but rather the upshot of a succession of coalitions of these specialists.
The basic specialists are part of our animal heritage. They were not developed to perform peculiarly human actions, such as reading and writing, but ducking, predator-avoiding, face-recognizing, grasping, throwing, berry-picking, and other essential tasks. They are often opportunistically enlisted in new roles, for which their nature talents more or less suit them. The result is not bedlam only because the trends that are imposed on all this activity are themselves the product of design. Some of this design is innate, and is shared with other animals. But it is augmented, and sometimes even overwhelmed in importance, by microhabits of thought that are developed in the individual, partly idiosyncratic results of self-exploration and partly the predesigned gifts of culture. Thousands of memes, mostly borne by language, but also by wordless “images” and other data structures, take up residence in an individual brain, shaping its tendencies and thereby turning it into a mind. (pp. 253-254)
Our tales are spun, but for the most part we don’t spin them; they spin us. Our human consciousness, and our narrative selfhood, is their product, not their source. (p. 418)
… the directives from mind to brain. These, ex hypothesi, are not physical; they are not light waves or sound waves or cosmic rays or streams of subatomical particles. No physical energy or mass is associated with them. How, then, do they get to make a difference to what happens in the brain cells they must affect, if the mind is to have any influence over the body? A fundamental principle of physics is that any change in the trajectory of any physical entity is an acceleration requiring the expenditure of energy, and where is this energy to come from? It is this principle of the conservation of energy that accounts for the physical impossibility of “perpetual motion machines,” and the same principle is apparently violated by dualism. This confrontation between quite standard physics and dualism has been endlessly discussed since Descartes’s own day, and is widely regarded as the inescapable and fatal flaw of dualism. (pp. 34-35)
Daniel Dennett is a prominent British philosopher who happens to be a vocal proponent of physicalism in the philosophy of mind. According to Dennett, the mind, the soul, does not strictly speaking exists. Rather, consciousness is a product of multiple biological processes in the brain that work together and give the illusion of a self, an individual. Consciousness is a "virtual machine" that comes into being by the interaction of the self with the cultural products known as "memes." In Dennett's words, the "thousands of memes... take up residence in an individual brain... turning it into a mind" (p. 254). Thus, there is no soul, no spirit, and consciousness itself is not a property (against property dualism) but a product of brain states and culture memes.
In his book Consciousness Explained, the main bulk of Dennett's writing is to argue against what he calls "Cartesian materialism," defined as a position that holds to both Dualism and Materialism. Substance dualism itself is rejected in a single paragraph in pages 34 and 35, as reproduced above, and not touched on again in the rest of the book. But what exactly is the argument against substance dualism? It turns out that the argument against substance dualism is an argument that makes sense only if we assume materialism. According to Dennett, if there are mental properties, then how can it be said that these mental properties interact with physical properties, if they have no energy, mass or wave function? In other words, if mental properties are not physical, they cannot interact with physical properties. Or, if there are mental properties, they cannot affect the physical neurons in the brain, and therefore there are no mental properties at all.
The problem with such an argument is that materialism is assumed to be true. If materialism is false, then the argument is in error as well. Even if we agree that the firing of the neurons must come about through physical causes, a rejection of materialism would result in a parallel process understanding of mental and physical processes. But we do not have to go there for the simple reason that there is no violation of any law of nature to say that a mental process calls for certain neurons to send electrical impulses across the brain. After all, what decides whether any particular neuron in a brain sends an electrical signal? Why does one neuron send an electrical signal and another nearby does not? Is there a physical explanation for that?
In conclusion, Dennett's dismissive argument against substance dualism is in error. It assumes materialism, which is not and cannot ever be proven true. Even the atheist Thomas Nagel was forced to reject materialism in his book Mind and Cosmos as he realized that materialism is not tenable. And just because mental properties cannot be empirically described does not make it false. We may not know exactly what mental properties are, but by virtue of us having a mind, we can give an approximate description for them.