The Nature of Consciousness

Piero Scaruffi

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These are excerpts and elaborations from my book "The Nature of Consciousness"

The Computational Theory of the Mind

The US philosopher Hilary Putnam (“Minds and Machines”, 1960) focused on the fact that the same mental state may be implemented by different physical states. For example, each person has a different brain, but every person has the same psychological states of "fear", "happiness", etc. Even other animals exhibit some of the same states. Putnam classified mental states based on their function, i.e. their causal roles within the mental system, regardless of their physical structure. Physical states and mental states can even be grouped in different ways.

Putnam then suggested that the psychological state of an individual  should be identified with the state of a so-called “Turing machine” (basically, with a computer). A psychological state would cause other psychological states according to the machine's operations. Belief and desire would correspond to formulas stored in two registers of the machine. Appropriate algorithms would process those contents to produce action.

Putnam’s idea led to a special case of identity theories, the “computational theory of the mind”.

The "representational theory of the mind", developed by the US linguist Jerry Fodor, is an evolution of Putnam’s ideas. Fodor argues that the mind is a symbolic processor. Knowledge of the world is embedded in mental representations, and mental representations are symbols, which possess their causal role in virtue of their syntactic properties (i.e., in virtue of how they can be used in “computing” operations). The mind is endowed with a set of rules to operate on such representations. Cognitive life is the transformation of those rules. The mind processes symbols without knowing what those symbols mean, in a purely syntactic fashion. Behavior is due only to the internal syntactic structures of the mind.

The symbols used to build mental representations belong to a language of thought, or "mentalese". Such language cannot be one of the languages we speak because the very ability to speak requires the existence of an internal language of representation. Such language is an intrinsic part of the brain and has been somehow produced through evolution. A belief, for example, is realized as a sentence in the language of thought which resides in the belief area of the brain ("I believe that my name is Piero" is implemented in the belief area by the translation in the language of thought of the English sentence "My name is Piero").

This inner language of thought is shared by all creatures capable of “propositional attitudes” (the simplest form of thought, such as beliefs, hopes, fears, desires). Such creatures can then express their representations in whichever human or animal language they happen to speak.

Fodor basically offers a solution to the problem faced by dualists: how to connect the mind and the body, mental states and physical states, the desire to do something and the act of doing it. Beliefs and desires are information, represented by symbols, and symbols are physical states of a processor, and the processor is connected to the muscles of the body. When the symbols change, they have an impact on the body, they cause behavior. At the same time, perception results in a change of those symbols. The processor, in turn, may change the symbols because it compacts several of them into a new one (reasoning). Mind and body communicate via symbol processing.

Fodor’s computational theory is consistent with those offered by the US linguist Noam Chomsky in linguistics and later by the British psychologist David Marr in vision: the mind as a set of modules that “compute” something based on an innate symbolic capability. Noam Chomsky spoke of "mental organs", to relate their role to the role of physical organs. Each organ carries out a function and communicates the results to the other organs.

Fodor generalizes their ideas: the mind is made of genetically-specified modules, each one specialized in performing one task. A module corresponds to a physical region of the brain, and is isolated from other modules. A module receives input only from modules of lower level, never from higher levels (for example, a belief cannot influence the working of a module that analyzes sensory data). Each module generates output in a common format, the "language of thought". Their outputs are input to the central processor, that manages long-term memory and manufactures beliefs. The central processor is the only module that is not domain-specific. Every other module deals with a specific domain.

Fodor does not seem to contemplate cognitive growth: the modules are fixed at birth and remain the same throughout the life of the individual.

The approach of the Canadian philosopher Stephen Stich is even more purely syntactic: he even rejects the notion that each object of a mental operation must represent something (or stand for something). Stich assumes that cognitive states correspond to syntactic states in such a way that causal relationships between syntactic states (or between syntactic states and stimuli and actions) correspond to syntactic relationships of corresponding syntactic objects. His “mind” is a purely syntactic program.

The US philosopher Ned Block believes that the psychological state of a person can be identified with the physical process that is taking place in the brain rather than the state in which the brain is. A psychological state can then be represented as an operation performed on a machine, i.e. identified with the computational state of the machine, rather than with its physical state. This way the psychological state does not depend on the physical state of the machine and can be the same for different machines that are in different physical states, but in which the same process is occurring.

Block has, actually, provided the broadest criticism of functionalism (“Troubles with Functionalism”, 1978). “Qualia” (sensations that are associated to the fact of being in a given psychological state) are not easily explained in a functionalist view. Take an organism whose functional states are identical to ours, but in which pain causes the sensation that we associate to pleasure (“inverted qualia”), and an organism whose functional states are identical to ours, but in which pain causes no sensation (“absent qualia”): functionalism cannot, apparently, account for either case. Furthermore, functionalism does not prescribe how we can limit the universe of organisms who have mental states. A functionalist might think that even Bolivia's economy, as expertly manipulated by a financier, has mental states.


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