Book Reviews

Additions to the Bibliography on Mind and Consciousness

compiled by Piero Scaruffi

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Paivio Allan: IMAGERY AND VERBAL PROCESSES (Holt, Rinehart and Winston, 1971)

Paivio was the first to posit that the mind must use two different types of representation, a verbal one and a visual one, corresponding to the brain's two main perceptive systems.

Parfit Derek: REASONS AND PERSONS (Oxford Univ Press, 1985)

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A survey of the field, from the split brain to connectionist models.

Pattee Howard Hunt: HIERARCHICAL THEORY (Brazillen, 1973)

Collects five essays. Herbet Simon's "The organization of complex systems" proves that hierarchical organization is pervasive Pattee's "The physical basis and origin of hierarchical control" proposes general principles of organization and asks for a physical theory of the origin of life that rely on such principles. One fundamental finding is that hierarchical control does not reside in any one level of the hierarchy, it operates between levels.

Pawlak Zdzislaw: ROUGH SETS (Kluwer Academic, 1991)

Rough sets are sets that are defined in terms of lower and upper bounds.. Rough sets are useful in classifying imprecise, uncertain or incomplete knowledge. The approximation space is a classification of the domain into disjoint categories. The lower approximation is a description of the objects that are known with certainty to belong to the domain. The upper approximation is a description of the objects that possibly belong to the domain.

Peacock Christopher: A STUDY OF CONCEPTS (MIT Press, 1992)

The book details Peacock's own theory of concepts.

Peak David & Frame Michael: CHAOS UNDER CONTROL (W.H.Freeman, 1994)

A textbook for beginners on complexity, with a good introduction to fractals.

Pearl Judea: HEURISTICS (Addison Wesley, 1984)

A well-organized and comprehensive technical textbook on heuristic methods for problem solving: hill climbing, best first algorithms, and so forth. The second part is an analysis of performance, the third part is devoted to game playing.

Pearce John: ANIMAL LEARNING AND COGNITION (Psychology Press, 1997)

A survey of a century of experiments on animals learning, memory and communication.


A property of information is that it is relevant for some other type of information. Relevance's dual property is dependence: if a piece of information is relevant to another piece of information, than this piece of information is dependent on the former. Relevance can be defined as "conditional independence". Pearl provides an axiomatic formulation of "conditional independence".
Pearl's causal networks (conditional dependency's graphical notation) are direct acyclical graphs in which nodes represent casual variables (which can have any value) and arcs express dependecies among them. By using Bayes' inversion formula the conditional probability of the nodes of the graph can be computed as information becomes available.
A causal net is isotropic, i.e. it can be used to perform inferences in both ways, top-down (to "predict" an event) and bottom-up (to "diagnose" an event).
Pearl thinks that experience is transformed into causal models so that it be possible for the mind to make decisions.
Pearl's belief function measures how close a proposition is to necessity, as opposed to classic probability which measures how close a proposition is to truth.

Peirce Charles: COLLECTED PAPERS (Harvard Univ Press, 1931)

Peirce devised a graphical notation to express logical relationships alternative to Peano's linear notation. Peirce then defined a set of operations to manipulate such graphs which conserve truth (equivalent to inference rules). Peirce's "existential graphs" can represent first-order predicate logic as well as modal logic (through colored contexts) and higher-order logics.
The theory of signs was originally developed by Charles Peirce and then revised by C.W. Morris.
A sign is something that stands for something else. Syntax is the study of the relations that signs bear to other signs. Semantics is the study of the relations that signs bear to what they stand for. Pragmatics is the study of the relations that signs bear to what they stand for and their users. Icons are signs that work by virtue of a relation of resemblance to what they stand for (e.g., photographs). Indices are signs that work by virtue of a relation of cause or effect with what they stand for. (e.g., dark clouds suggest rain). Symbols are signs that work by virtue of a conventional association to what they stand for (numbers, nouns, etc). For all three categories of signs, types are kinds of things, tokens are their instances.

Penfield Wilder: MYSTERY OF THE MIND (Princeton Univ Press, 1975)

Penfield showed that memory is distributed in the brain.

Penrose Roger: THE EMPEROR'S NEW MIND (Oxford Univ Press, 1989)

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Penrose Roger: SHADOWS OF THE MIND (Oxford University Press, 1994)

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Penrose Roger: THE LARGE THE SMALL AND THE HUMAN MIND (Cambridge Univ Press, 1997)

Penrose rehashes his theory of the universe and his theory of consciousness, and responds to criticism by distinguished colleagues. Goedel's theorem implies that thinking must be non-computational. Penrose carefully separates determinism from computation and looks for a deterministic but noncomputational solution to the puzzle of consciousness. The solution lies in "objective reduction", a type of collapse of the wave function which occurs when the universe must choose between significantly differing spacetime geometries. Objective reduction controls the operation of the brain through its effects on coherent flows inside microtubules of the cytoskeleton.

Penrose Roger: THE ROAD TO REALITY (Oxford University Press, 2004)

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Pereira Nelson & Grosz Barbara: Natural Language Processing (MIT Press, 1994)

A collection of articles from the Journal of Artificial Intelligence.

Piaget Jean: EQUILIBRATION OF COGNITIVE STRUCTURES (University of Chicago Press, 1985)

Piaget's theory of knowledge (or genetic epistemology) Knowledge is constructed by each individual through her interaction with the environment, knowledge is a developing relationship between the individual and her environment. Knowledge is not simply absorbed, but it is also organized, for the purpose of adaptation. Knowledge develops through a process of self-organization based on feedback from the environment. The goal is to reach a sequence of progressive states of equilibrium through a process of "equilibration". Development is viewed as a progressive equilibration leading from a lesser to a higher state of equilibrium, i.e. as a progressive increase in equilibrium. The passage from one equilibrium state to the next is driven by maturation (physiological growth of hereditary structures), experience and social transmission, besides equilibration.
At different ages (developmental stages) the child exhibits different knowledge structures. The stage of sensory-motor behavior include: a stage of hereditary reflexes, a stage of acquired adaptations (one to four months), a stage of circular reactions (four to eight months), a stage of intentional behavior (eight to twelve months), a stage of directed groping (twelve to eighteen months), a stage of symbolic representation (eighteen to tweentyfour months). Through them the individual develops from a biological organism to a social one.
At this point the child is beginning to symbolize. Thoughts are actions that take place in the mind, and Piaget calls them "operations". At this point cognitive development begins. From concrete operations (seven-twelve years) the child moves on to formal operations (twelve-fifteen years) and eventually to the hypothetico-deductive thinking of adults. The construction of stages proceeds according to a law of temporal displacement, i.e. it is a nonlinear process of continous reconstruction of the constructions of earlier stages (relearning) at a higher level. This reconstruction provokes reflective abstraction, or reorganization of knowledge at a higher level.
Cognitive structures are forms of equilibrium between the individual and the environment. At each stage of development the process of equilibration is repeated. At each stage of equilibrium there is an urge toward adaptation based on feedback from the environment. At every cycle the structures of thought ("structures d'ensemble") become more sophisticated. Progress is driven by the need to find solutions to current problems and anticipating possible ones.
In the process of cognitive development a number of events occur: decentration (the individual becomes less and less egocentric), internalization (of action), temporal displacement, reflective abstraction, and awareness. Following Claparede, Piaget thinks that as long as the individual can cope with the environment she does not develop self-consciousness.

Pinker, Steven: WORDS AND RULES (Basic, 1999)

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Pinker Steven: HOW THE MIND WORKS (Norton, 1997)

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Pinker Steven: THE LANGUAGE INSTINCT (William Morrow, 1994)

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Pinker, Steven: THE BLANK SLATE (Viking, 2002)

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Pinker Steven: THE STUFF OF LANGUAGE (Viking, 2007)

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Platts Mark: WAYS OF MEANING (MIT Press, 1997)

An introduction to philosophy of language.

Plotkin Henry: DARWIN MACHINES AND THE NATURE OF KNOWLEDGE (Harvard University Press, 1994)

The British psychologist Henry Plotkin defines knowledge as incorporating the knower. His focus is on the harmony established over the centuries between the organization and structure of a living being and the world it inhabits. Adaptation is the act of incorporating the outside world into the organism's structure and organization. More properly, this is "biological" knowledge. But human knowledge is simply a subset of biological knowledge. Plotkin therefore advocates a science of knowledge that would be based on evolutionary theory. Darwinism is likely to become the basis of all science, the idea spreading beyond biological evolution. Plotkin views brains themselves as Darwin Machines (just like Calvin). "Universal darwinism" will be a theory based on darwinism but general enough to encompass everything. A likely candidate structure for an empirical science is one based on the concepts of replicator (an entity that can make copies of itself) and interactor (an entity that can propagate replicators in space and conserve them in time while interacting with the environment). The presence of this combination is evidence that evolutionary algorithms are at work. They occur in life, in the brain, in the immune system, in memes.


A collection of essays that deal with behavior as a cause of evolution. Evolution determines behavior, but Plotkin and others believe that, in turn, behavior determines evolution. In 1960 the British biologist Conrad Hal Waddington pointed out that animals can choose the environment where they will live and therefore pass on to future generations a new class of selective pressures, indirectly influencing their evolution. Plotkin builds upon Waddington's intuition. What an individual does affects the evolution of its species. Individual behavior causes an acceleration in population evolution because it exposes the phenotype to a broader range of selection pressures than it would otherwise not experience.
David Hull discusses interactors and replicators in general. Replicators are units that reproduce their structure directly. Interactors are entities that interact directly with their environment. The difference between Hull's interactors and Dawkins' "vehicles" is not trivial: genes are both replicators and interactors (they have a physical structure that interacts with an environment), and some interactors are also replicators (the paramecium that splits in two).
Robert Brandon, inspired by Lewontin and others, offers a hierarchy of interactors. The biosphere is hierarchically arranged and selection operates at all levels.
Robert Brandon defines natural selection as the process of differential reproduction due to differential fitness to a common selective environment. The "selective" environment (measured in terms of the relative fitnesses of different genotypes across time or space) is distinguished from the "external" environment and the "ecological" environment (measured using the organism itself as the measuring instrument so that only that part of the external environment that affects the organism's contribution to population growth is taken into account). The selective environment is the one that is responsible for natural selection.

Plotkin Henry: EVOLUTION IN MIND (Allen Lane, 1997)

Plotkin provides a delightful introduction to evolutionary psychology via ethology and sociobiology, assuming the tenet that most of an animal's behavior is functional to survival and hard-coded in its genes by evolution (we are "bundles of adaptations"). Nurture has nature: predispositions form and then execute. The book reviews several theories by contemporary thinkers to frame the borders of evolutionary psychology, from child development to Dawkins' memes.


A collection of essays on evolutionary epistemology (evolution as a knowledge process) and classic papers on evolution (Bateson, Campbell, Popper, Lorenz, Mayr, Piaget, Waddington, Williams). founded by Donald Campbell on pioneering ideas by Popper similarities between bioogical and sociocultural evolution

Polya George: MATHEMATICS AND PLAUSIBLE REASONING (Princeton Univ Press, 1954)

A multi-volume survey of plausible reasoning. Plausible reasoning is what supports and yields human knowledge of the world, as opposed to demonstrative reasoning, which is incapable of yielding new knowledge.
Volume one is devoted to induction and analogy. Volume two is devoted to patterns of plausible inference, nondemonstrative thinking and the theory of probability.

Plotkin Henry: EVOLUTION IN MIND (Allen Lane, 1997)

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Polya George: COLLECTED PAPERS (MIT Press, 1974)

Four volumes of collected papers.

Polya George: HOW TO SOLVE IT (Doubleday, 1957)

This thin book summarizes Polya's studies on the methods of solving mathematical problems. Polya's mathematics is not a monolotic deductive system in which the mathematician is a mindless machine performing mechanic operations, but an open game in which the mathematician must create a plan for achieving the desired solution. The book is written as a tool for teachers and students, but it really offers a comprehensive analysis of heuristic reasoning, from analogy to generate and test.

Polya George: MATHEMATICAL DISCOVERY (Wiley, 1965)

A textbook on understanding, learning and teaching problem solving. Polya defines "heuristic" the study of the methods for problem solving. Polya describes general, recurring patterns of behavior in trying to solve problems.

Popper Karl: THE LOGIC OF SCIENTIFIC DISCOVERY (Hutchinson, 1959)

Popper challenged logical positivism's hypothetico-deductive model of theory formation. Criticizing any inductive form of reasoning that attempts to derive a general proposition from specific instances, Popper proposes to focus on demonstrating that hypotheses are false. The scientific process should be one of conjectures and refutations.

Popper Karl & Eccles John: THE SELF AND ITS BRAIN (Springer-Verlag, 1977)

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Popper Karl: KNOWLEDGE AND THE BODY-MIND PROBLEM (Routledge, 1994)

In these lectures Popper recapitulates his theory of the mind.
Popper distinguishes objective knowledge ("I know that water is liquid") from subjective knowledge ("I know that I am wrong").
Popper posits the existence of a first world (the world of physical bodies), a second world (the world of mental states) and a third world (the world of products of the mind). The second world communicates with both the others.
Objective knowledge belongs to the third world. The third world evolves through the growth of objective knowledge. Objective knowledge confers a degree of autonomy to the third world (numbers are created by the mind, but then mathematical laws determine what happens to them, regardless of the mind). Popper derives biological phenomena of survival and evolution from the same formula that determines the growth and evolution of objective knowledge (basically, trial and error).
Consciousness emerged evolutionary with the faculty of language. Consciousness emerges during growth with the faculty of language. Therefore it must be related to the brain region that deals with speech.

Porges Stephen & etc.: PSYCHOPHYSIOLOGY SYSTEMS PROCESS (Guilford, 1986)

A collection of articles on psychophysiology, a close relative of cognitive neuroscience which investigates psychological phenomena from their physiological bases. Chapters are devoted to attention, memory, learning, emotion, stress, sexuality.

Port Robert & Van Gelder Timothy: MIND AS MOTION (MIT Press, 1995)

A collection of papers on the dynamical approach to cognition.


A monumental, comprehensive introduction to the field by a number of distinguished authors. Includes chapters on cognitive architectures (such as ACT and SOAR), connectionism, model-theoretic semantics, neurophysiology, discourse, mental models, vision, memory, action, etc.

Power Michael: COGNITION AND EMOTION (Psychology Press, 1997)

A survey of philosophical and psychological studies on the relationship between emotion and cognition, with an attempt to integrate the two.

Priest Stephen: THEORIES OF MIND (Houghton Mifflin, 1991)

Priest provides a good, scholastic, down-to-earth coverage of dualism (Plato and Descartes), monism (Spinoza, Russell), behaviorism (Hempel, Ryle, Wittgenstein) idealism (Berkeley, Hegel), materialism (Place, Davidson, Honderich, Putnam, Lewis) and phenomenology (Husserl).

Pribram Karl: LANGUAGES OF THE BRAIN (Prentice Hall, 1971)

Pribram's holonomic model of memory is based on the hologram. Memory is distributed in the brain. Memories do not disappear all of a sudden, but slowly fade away. This is consistent with Penfield's experiments.
A sensory perception is transformed in a "brain wave", a scheme of electrical activation that propagates through the brain just like the wavefront in a liquid. This crossing of the brain provides the interpretation of the sensory perception in the form of a "memory wave", which in turn crosses the brain. The various waves that travel through the brain can interfere. The interference of a memory wave and a visual wave generates a structure that resembles an hologram.
Consciousness is due to fields within the cerebral hemispheres. Because of the physical properties of fields, they can store information in a form analogous to holograms.

Pribram Karl & Eccles John: RETHINKING NEURAL NETWORKS (Lawrence Erlbaum, 1993)

Proceedings of a conference on neurodynamics. Includes R.L. Dawes' "Advances in the theory of quantum neurodynamics".

Pribram Karl: BRAIN AND PERCEPTION (Lawrence Erlbaum, 1990)

A collection of lectures that review Pribram's holographic (or, better, "holonomic") theory of the brain.
The theory employs Fourier transformations to deal with the dualism between spacetime and spectrum, and Gabor's phase space to embed spacetime and spectrum. All perceptions (and not only colors or sounds) can be analyzed into their component frequencies of oscillation and therefore treated by Fourier analysis. Dirac's "least action principle" (which favors the least expenditure of energy) constrains trajectories in such a space. Gabor's uncertainty principle sets a limit with which both frequency and spacetime can be concurrently determined (the fundamental minimum is Gabor's "quantum of information").
A rigorous description of transformations leading from perceptions to feature extraction is provided for a variety of visual and cognitive activities. Processes local to specific brain regions are studied in neurophysiological detail.
Pribram expresses a few innovative viewpoints along the way. Both distributed and localized functions characterize brain functions. Structure and process are two aspects of the same entity, distinguished only by the scale of observation (from a distance an entity looks like a structure, but close enough it is a process). The formalism of quantum theory applies to the modeling of brain functions such as vision (brain microprocesses and physical microprocesses can be described by the same formalism).

Pribram Karl: ORIGINS (Lawrence Erlbaum, 1994)

Proceedings of a conference on neurodynamics. Contributions by Prigogine ("mind and matter: beyond the cartesian dualism"), P.J. Werbos ("self-organization"), J. Gyr ("psychophysics"), C. Game ("non-equilibrium thermodynamics and the brain"), and neurophysiological models.

Pribram Karl & Broadbent Donald: BIOLOGY OF MEMORY (Academic Press, 1970)

A collection of articles on models of memory. It includes Endel Tulving on different retrieval mechanisms for short- and long-term memories.

Price Huw: TIME'S ARROW AND ARCHIMEDE'S POINT (Oxford University Press, 1996)

The australian philosopher Huw Price advances a solution to the biggest dilemma of Quantum Physics: the mystery of the collapse of the wave function. He starts by examining asymmetry in Physics: the asymmetry of Thermodynamics, due to the second law, the asymmetry of radiation and the asymmetry of cosmology (entropy was very low at the beginning, will be very high at the end). Richard Feynman and John Wheeler had offered an explanation to unify all asymmetries, but Price thinks that all asymmetries must instead be reduced to a fundamentally coordinated behavior of the universe. The preferred direction from the past to the future is due to the fact that our universe contains sources of coordinated behavior. Nonetheless, Price believes that our theories are asymettric because we are conditioned by folk concepts of causality. Physical theories are built starting with the assumption that the future cannot influence the past, and therefore it is no surprise that they prescribe that the future cannot influence the past. Price thinks that backward causation (that future can influence the past), or advanced action, is a legitime option. By using it, one redraws the laws of Quantum Physics and finds that Einstein was right with his hypothesis of hidden variables, that Quantum Physics provides an incomplete description of the universe. A complete Quantum Physics will not assign any critical role to the observer.

Priest, Stephen: THEORIES OF THE MIND (Houghton Mifflin, 1991)

A collection of seminal papers on the various schools of philosophy of mind (materialism, dualism, behaviorism, etc).

Prigogine Ilya: THE END OF CERTAINTY (Simon & Schuster, 1997)

Prigogine investigates the role of irreversibility in nature. The arrow of time, as expressed by biological, geological and cosmological evolution, is not only a subjective illusion, it is a fundamental property of nature. A widespread interpretation of macroscopic irreversibility of things is that it simply arises from our ignorance of the microscopic state of things. Prigogine counters this argument by stating that unstable systems are real and that it is instability that breaks the symmetry of time. It does so because instability requires probability (the evolution of an unstable state can only be described as a range of probable evolutions) and probabilities introduce irreversibility. Stable systems allow for certitude, but unstable systems only allow for probabilities, and probabilities cannot be undone. Instability also solves the dilemma of the quantum observer: it is not the observer that breaks the symmetry of time, it is the instability related to the observation. The Prigogine shows that, far from being an illusion, the arrow of time is a source of order in nature.


Prigogine introduced the minimum entropy principle (stable near-equilibrium dissipative systems minimize their rate of entropy production) to characterize living organisms.


In classical and quantum Physics, equations are invariant with respect to time inversion. Future and past are equivalent. Time is only slightly different from space. Time is therefore a mere geometrical parameter. And Physics offers a static view of the universe. The second law of Thermodynamics made official what was already obvious: that many phenomena are not reversible, that time is not merely a coordinate in space-time. Irreversible processes are not only ubiquitous but they also play a fundamental role in biological phenomena.
Prigogine shows, using Boltzmann's theorem, that irreversibility is the manifestation at macroscopic level of randomness at microscopic level.
A theory of "instability", based on Aleksander Lyapounov's, is made necessary by two observations: that classical Thermodynamics is about destruction of structure, while structures spontaneously appear in nature; and that near instabilities large fluctuations invalidate probability theory (upon which Thermodynamics is founded).
Prigogine attempts a microscopic formulation of the irreversibility of laws of nature. He associates macroscopic entropy (or Lyapounov functions) with a microscopic entropy operator. Time too becomes an operator, no longer a mere parameter. Both time and entropy are therefore operators. This way, Prigogine turns the table around: instead of having a basic theory expressed in terms of wave functions (i.e., of individual trajectories), he obtains a basic theory in terms of distribution functions (i.e., bundles of trajectories). Time itself depends on the distribution and therefore becomes itself a stochastic quantity, just like entropy, an average over individual times. As a consequence, just like entropy cannot be reversed, time cannot: the future cannot predicted from the past anymore.
This formulation unifies physical and biological phenomena. Traditionally, physical space is geometrical, biological space (the space in which biological form develops) is functional (for example, physical time is invariant with respect to rotations and translations, biological space is not).
This is the concept of time used by Nicholis and Prigogine in their "bifurcation theory" (Thom's catastrophe theory being a particular case).

Prigogine Ilya & Stengers Isabelle: ORDER OUT OF CHAOS (Bantham, 1984)

This is the english edition of "La Nouvelle Alliance" (1979). Prigogine analyzes the history of science and scientific thought and derives a new vision of the world.
Living organisms function as dissipative structures, structures that form as patterns in the energy flow and that have the capacity for self-organization in the face of environmental fluctuations. Dissipative systems maintain their structure by continous dissipation of energy.
Classical science (and quantum mechanics) describes a world as a static and reversible system that undergoes no evolution, whose information is constant in time. On the other hand the second law of thermodynamics describes the world as evolving from order to disorder, while biological evolution is about the complex emerging from the simple (structure, i.e. order, arises from disorder). Irreversible processes are an essential part of the universe. Conditions far from equilibrium foster phenomena such as life that classical physics does not cover.
Prigogine focuses on the peculiar properties exhibited by systems far from equilibrium.
Non-equilibrium conditions favor the spontaneous development of self-organizing systems (i.e., dissipative structures), which maintain their internal organization, regardless of the general increase in entropy, by expelling matter and energy in the environment. Most of Nature is made of dissipative systems, of systems subject to fluxes of energy and/or matter. Dissipative systems conserve their identity thanks to the interaction with the external world.
The concept of organization is deeply rooted in the physical universe.
Prigogine considers living organisms as dissipative structures in states of non-equilibrium. A system that is not in equilibrium exhibits a variation of entropy which is the sum of the variations of entropy due to the internal source of entropy plus the variation of entropy due to the interaction with the external world. The former is positive, but the latter can equally be negative. Therefore total entropy can decrease.
An organism "lives" becausa it absorbs energy from the external world and processes it to generate an internal state of lower entropy. An organism "lives" as long as it can avoid falling in the equilibrium state.
Probability and irreversibility are closely related. Boltzman had already proved that entropy grows because probability grows.

Prior Arthur: PAST, PRESENT AND FUTURE (Clarendon Press, 1967)

Prior's temporal logic assumes that the temporal reference is negligible and therefore provides an underlying theory for an instant-based ontology (as opposed to the interval-based ontology) of Time.
Time is formalized by means of modal operators that express properties such as "always" and "sometimes", "before" and "after", "while" and "when". Prior's theory finds a logical correspondent to many past and future tenses by reducing them to two fundamental modal operators, one for the past and one for the future. Nonetheless, Prior cannot represent "since" and "until", which can easily be expressed by classical logic.

Prior Arthur: WORLDS, TIMES, AND SELVES (Duckworth, 1977)

Prior investigates structural analogies between modal logic (the formal study of necessity and possibility) and quantification theory (the formal study of universality and existentiality) and develops a modal system Q with an operator Q that picks out instants, worlds, or selves, as the case may be.

Purves Dale: NEURAL ACTIVITY AND THE GROWTH OF THE BRAIN (Cambridge Univ Press, 1994)

Brain cells are in a continual state of flux, creating and destroying synapses all the time. Neural activity caused by external stimuli is responsible for the continual growth of the brain, and for sculpting a unique brain anatomy in every individual based on the individual's experience.

Putnam Hilary: MIND, LANGUAGE AND REALITY (Cambridge Univ Press, 1975)

The same mental state may be implemented by different physical states.
Putnam imagines a world called "Twin Earth" exactly like Earth in every respect except that the stuff which appears and behaves like water, and is actually called "water", on Twin Earth is a chemical compound XYZ. If one Earth and one Twin Earth inhabitant, identical in all respects, think about "water", they are thinking about two different things, while their mental states are absolutely identical. Therefore the content of a concept depends on the context ("externalism"). Meanings are not in the mind, they also depend on the objects that the mind is connected to.
Putnam classifies mental states based on their function, i.e. their causal roles withing the mental system, regardless of their physical structure. Putnam originally suggested that the psychological state of an individual be identified with the state of a Turing machine. A psychological state would cause other psychological states according to the machine's operations. Belief and desire correspond to formulas stored in two registers of the machine. Appropriate algorithms process those contents to produce action.

Putnam Hilary: REASON, TRUTH AND HISTORY (Cambridge Univ Press, 1981)

Putnam provides a formal proof that model-theoretic semantics fails as a theory of meaning, because he found a fundamental contradiction between the definition of meaning in model theory (a function which assigns a truth value to a sentence for all possible cases) and the constraint that the meaning of the parts cannot be changed without changing the meaning of the whole. Putnam proves that meaning does not stand in the realtionship between symbols and the world.
His criticism of symbol systems is based on the observation that, since we are part of reality, there can be no complete and true description of the world: we are part of the reality that we observe, we cannot claim the role of independent observer.
The definition of truth depends on the meaning of the words of the language and each definition of truth should list all conditions that meaning depends on (including the definition of truth which is being defined).


Putnam abandons his functionalist theory of the brain.
Mind cannot comprehend itself. An automaton cannot explain its own behavior. The same mental state may be implemented by different computational (functional) states, therefore mental states cannot be computer programs.
Explanation and prediction of intentional phenomena such as belief and desire belong to the realm of interpretation: concepts do not exist in the mind, are the output of interpretation. Interpretation can be "normative", when it employs Davidson's principle of charity or Dennett's principle of "rationality", which state that an organism behaves as it should given the circumstances (most of its beliefs are true, it believes in the implications of its beliefs, no two beliefs contradict each other, and so on); or "projective" (Stitch), when it attributes to an organism the propositional attitudes that we would have were we in its situation.
Meaning exhibits an identity through time but not in its essence (such as momentum, which is a different thing for Newton and Einstein but expresses the same concept). An individual's concepts are not scientific and depend on the environment. Most people know what gold is, and still they cannot explain what it is and even need a jeweler to assess whether something is really gold or a fake. Still, if some day we found out that Chemistry has erred in counting the electrons of the atom of gold, this would not change what it is. The meaning of the word "gold" is not its scientific definition, but the social meaning that a community has given it. It is not true that every individual has in its mind all the knowledge needed to understand the referent of a word. There is a subdivision of competence among human beings and the referent of a word is due to their cooperation. Meaning is not in the mind.

Pylkkanen Paavo: MIND, MATTER AND ACTIVE INFORMATION (Univ. of Helsinki, 1992)

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Pylyshyn Zenon: COMPUTATION AND COGNITION (MIT Press, 1984)

Zenon Pylyshyn believes in a variant of Fodor's language of thought. He has applied that theory to the debate on mental imagery, his "descriptionalism" being opposed to Stephen Kosslyn's pictorialism.
Pylyshyn recognizes three levels of description for cognitive tasks: the knowledge level (which explains actions of the system as functions of what it knows and its goals), the symbolic level (which codifies the semantic content of the knowledge and the goals), and the physical level. Unlike Marr, Pylyshyn believes that all three levels must be studied to understand cognitive functions.
The primitive operations of the mind's cognitive architecture can be recognized because they are those defined solely by the biology of the brain, that is those that cannot be altered by no other cognitive activity, that are "cognitively impenetrable".
Images are simply the product of the manipulations of knowledge encoded in the form of propositions.

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