The Engine of Reason, the Seat of the Soul Analysis

Paul M. Churchland

Context

In the seventeenth century, French philosopher René Descartes argued that humans have an immaterial mind (also called “soul” or “self” or “spirit”) over and above the material brain. This position is known as mind-body dualism. The mind is the origin of thought (“the engine of reason”) as well as “the seat of the soul.” For Descartes, the mind causally interacts with the brain, although this interaction is difficult to explain. Modern dualists have not been successful either, and this problem has led many philosophers, psychologists, and cognitive scientists in general (such as neuroanatomists, neurochemists, artificial intelligence researchers, scientifically trained philosophers) to argue for materialism, the view that denies there is such an entity as “the mind” and claims that there is only one entity, the material brain. In The Engine of Reason, the Seat of the Soul, Paul M. Churchland holds this position, a position supported by studies on brain-damaged and brain-lesioned patients. For example, postmortem examinations of the brains of people who had Alzheimer’s disease reveal material plaques and tangles throughout the fine web of synaptic connections of the neurons of the brain that embodies all of one’s cognitive skills and capacities for recognition.

Moreover, Churchland is impressed with the tremendous advances in the neurosciences and in AI research that allows modeling of brain processes. Modeling enables cognitive scientists to represent brain function as massively parallel distributive processing (PDP) of recurrent neural nets that carry out vector-to-vector transformations or vector completions. This model (perhaps theory) of human cognitive brain processes will effect, Churchland claims, a revolution in understanding of the self, consciousness, all cognitive processes, science, art, and much else besides. His book is intended to convey the possibilities and excitement of this revolution.

Churchland’s book is divided into two parts. Part 1 describes the enormous anatomical complexity of the brain and links this complexity to artificial neural networks in computer modeling that imitate parts of the brain. Part 2 explores the consequences of this neuroscientific approach to cognition and soul and, in the process, delves into the nature of consciousness and shows how the new neuroscientific approach can be applied in many other domains besides the study of consciousness, such as science, philosophy, ethics, law, and medicine.

The Brain

Churchland begins by describing the enormous structural capacity of the human brain to represent the world. For example, a standard television screen contains about 200,000 pixels, the tiny dotlike elements that are easily seen if one peers very closely at the screen. However, the human brain has approximately 100 billion nerve cells, or neurons, each of which can also take on a full range of activation levels (or “brightness values” when compared to pixels). Counting each neuron as a pixel, one can calculate that the brain’s representational capacity is about 500,000 times greater than a television screen’s representational capacity.

Churchland then asks the reader to consider one of the twin towers of the World Trade Center in New York City. Imagine the entire outside surface—all 500,000 square feet of the skyscraper—to be tiled with 500,000 television screens so that each seventeen-inch screen is glued next to each other and facing outward. Assuming there are about 200,000 pixels per square foot, one can calculate that there are 100 billion pixels in this setup that correspond to the 100 billion neurons in the human brain. This is the minimum visual representational power of the human brain, for the brain can also represent reality in many other dimensions, including, for example, social, moral, and emotional.

Churchland then asks the reader to picture that the skyscraper’s pixels are embedded in a thin sheet of...

(The entire section is 513 words.)

Cognition

Churchland turns to a discussion of cognition, which involves learning or “training up a network.” One famous example concerns a submarine’s sonar system detecting the difference between a mine echo or a rock echo. The sonar system network contains thirteen sonar input cells, and each cell codes the total energy contained in the sonar echo at exactly one of the thirteen sampled frequencies. Each echo is thus characterized by a distinct activation vector across the input population of cells. The cells of the sonar machine at the input layer all project to a second layer and then on to a third layer that consists of only two cells, whose job it is to signal mine or rock, as the case may be. This is also called “vector-to-vector transformation.” If the output vector relaxes into a final configuration of (1,0), or close to this, then the sonar has detected a potentially dangerous, explosive mine; when the final configuration is (0,1), or close to this, the sonar has detected a harmless rock.

As the network is trained up, scientists initially have no idea how to configure its connection weights. Hoping to get lucky, they set the weights at small random values and prepare to teach the network on a substantial training set of recorded sonar echoes, half of them returned from real mines placed by the scientists on the ocean floor and half of them returned from visually identified rocks. Using a well-known method of back propagation of synaptic weight adjustments, the scientists cycle the information repeatedly through the training set until the network has assumed an overall synaptic weight adjustment that minimizes the mean squared...

(The entire section is 673 words.)

Consciousness

In part 2, Churchland deals with the fascinating but difficult puzzle of consciousness. This phenomenon appears unique to human beings and beyond scientific and purely physical explanation. Traditionally, philosophers have argued that the phenomenon is basically a subjective occurrence, accessible only to the creature that has it. Churchland argues against this classical view.

Churchland begins by reviewing a number of similar arguments for the classical view advanced by philosophers such as Gottfried Wilhelm Leibniz, Thomas Nagel, John Searle, and Frank Jackson. Nagel’s argument was advanced in his seminal 1974 paper, “What Is It Like to Be a Bat?” Nagel argues that no matter how much one might know about the neuroanatomy of a bat’s brain and the neurophysiology of a bat’s sensory apparatus, one will never know “what it would be like” to have the bat’s sensory experience. Even if scientists could track the neuroactivation patterns, one would never know what they are like from the unique perspective of the creature that possesses them; their intrinsic character as felt experiences would still be unknown to us. A purely physical science of the brain, Nagel and others argue, does have a limit on the capacity of understanding as it reaches the subjective character of the contents of one’s consciousness.

Churchland responds by arguing that Nagel fails to make a distinction between how one knows...

(The entire section is 503 words.)

Additional Reading

America. CLXXIII, December 16, 1995, p. 24.

Bechtel, William. “What Should a Connectionist Philosophy of Science Look Like?” In The Churchlands and Their Critics, edited by Robert N. McCauley. Oxford, England: Blackwell Scientific Publications, 1996. The author is also a major figure in the field of philosophy and cognitive science. He holds that traditional philosophy of science has been little concerned with the psychology of science, and that the general sentential approach of traditional philosophy of science is ineffective. Bechtel nevertheless questions Paul M. Churchland’s claim that theories and explanations are best understood in terms of representations in the heads of scientists.

Choice. XXXIII, December, 1995, p. 634.

Clark, Andy. “Dealing in Futures: Folk Psychology and the Role of Representations in Cognitive Science.” In The Churchlands and Their Critics, edited by Robert N. McCauley. Oxford, England: Blackwell Scientific Publications, 1996. This article is written by another major leader in the field of philosophy and cognitive science. Clark agrees with the Churchlands that connectionist models can contribute very valuable, new resources for understanding human cognition. However, he forcefully rejects Churchland’s claim that this outcome impugns folk psychology.

Flanagan, Owen. “The Moral Network.” In The Churchlands and Their Critics, edited...

(The entire section is 530 words.)

Bibliography

Additional Reading

America. CLXXIII, December 16, 1995, p. 24.

Bechtel, William. “What Should a Connectionist Philosophy of Science Look Like?” In The Churchlands and Their Critics, edited by Robert N. McCauley. Oxford, England: Blackwell Scientific Publications, 1996. The author is also a major figure in the field of philosophy and cognitive science. He holds that traditional philosophy of science has been little concerned with the psychology of science, and that the general sentential approach of traditional philosophy of science is ineffective. Bechtel nevertheless questions Paul M. Churchland’s claim...

(The entire section is 532 words.)