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Free Energy and the Brain
  • Literature Review
  • Full-text available

January 2008


917 Reads


Klaas E Stephan
If one formulates Helmholtz's ideas about perception in terms of modern-day theories one arrives at a model of perceptual inference and learning that can explain a remarkable range of neurobiological facts. Using constructs from statistical physics it can be shown that the problems of inferring what cause our sensory input and learning causal regularities in the sensorium can be resolved using exactly the same principles. Furthermore, inference and learning can proceed in a biologically plausible fashion. The ensuing scheme rests on Empirical Bayes and hierarchical models of how sensory information is generated. The use of hierarchical models enables the brain to construct prior expectations in a dynamic and context-sensitive fashion. This scheme provides a principled way to understand many aspects of the brain's organisation and responses.In this paper, we suggest that these perceptual processes are just one emergent property of systems that conform to a free-energy principle. The free-energy considered here represents a bound on the surprise inherent in any exchange with the environment, under expectations encoded by its state or configuration. A system can minimise free-energy by changing its configuration to change the way it samples the environment, or to change its expectations. These changes correspond to action and perception respectively and lead to an adaptive exchange with the environment that is characteristic of biological systems. This treatment implies that the system's state and structure encode an implicit and probabilistic model of the environment. We will look at models entailed by the brain and how minimisation of free-energy can explain its dynamics and structure.

Philosophical conceptions of rationality and psychiatric notions of competency

December 1983


18 Reads

Psychiatrists are frequently called upon to make assessments of the rationality or irrationality of persons for a variety of medical-legal purposes. A key category is that of evaluations of a patient's capacity to grant informed consent for a medical procedure. A diagnosis of mental illness is neither a necessary nor a sufficient condition for a finding of incompetence. The notion of competency to grant consent, which is a mixed psychiatric-legal concept, shares some features with philosophical conceptions of rationality, but differs from them in a number of important respects. This article describes the actual practice of psychiatrists when making such judgments, along with the standards of competency they employ. A comparison is made between those notions of competency and predominant philosophical conceptions of rationality.

Real Knowledge

May 1983


17 Reads

Philosophers have sought to characterize a type of knowledge — what I call real knowledge — which is significantly different from the ordinary concept of knowledge. The concept of knowledge as true, justified belief — what I call knowledge simpliciter — failed to depict the sought after real knowledge because the necessary and jointly sufficient conditions of knowledge simpliciter can be felicitously but accidentally fulfilled. Real knowledge is knowledge simpliciter plus a set of requirements which guarantee that the truth, belief and justification conditions are not accidentally conjoined. Two of those requirements have received considerable attention in recent literature by the defeasibility theorists and the causal theorists. I argue that a third requirement is needed to block the merely coincidental cosatisfaction of the belief and justification conditions and to capture our intuitions about the epistemic agent who possesses real knowledge. That condition ascribes a disposition to the real knower to believe all and only justified propositions in virtue of his/her belief that the propositions are justified. Two consequences of that requirement are discussed: (1) if S really knows that p, then S knows simpliciter that S knows simpliciter that p and (2) the iterative feature of real knowledge mentioned in (1) provides a basis for the rejection of a particularly pernicious form of scepticism.

Human Understanding

April 1990


6 Reads

Contemporary thinkers either hold that meanings cannot be mental states, or that they are patterns of brain functions. But patterns of social, or brain, interactions cannot be that which we understand. Wittgenstein had another answer (not the one attributed to him by writers who ignore his work in psychology): understanding, he said, is seeing an item as embodying a type Q, thus constraining what items will be seen as “the same”. Those who cannot see things under an aspect are meaning-blind. That idea is expanded in this article. Its ontology consists of types only: entities that recur in space, time, and possible worlds. Types (Socrates, Man, Red, On, etc.) overlap; Socrates = Bald at some index and not in another. The logic used is thus that of contingent identity. Now some possible worlds are mentally represented; the entities that occur in them are meanings. But such entities may also recur in the real world. Thus the entities we experience, the phenomena, which serve as our meanings, may be identical in the real world with real things. A correspondence theory of truth is thus developed: a sentence is true iff its meaning constitutes, in a specified way, a real situation.

Some local models for correlation experiments

February 1982


15 Reads

This paper constructs two classes of models for the quantum correlation experiments used to test the Bell-type inequalities, synchronization models and prism models. Both classes employ deterministic hidden variables, satisfy the causal requirements of physical locality, and yield precisely the quantum mechanical statistics. In the synchronization models, the joint probabilities, for each emission, do not factor in the manner of stochastic independence, showing that such factorizability is not required for locality. In the prism models the observables are not random variables over a common space; hence these models throw into question the entire random variables idiom of the literature. Both classes of models appear to be testable.

On Individual Risk

September 2017


492 Reads

We survey a variety of possible explications of the term "Individual Risk." These in turn are based on a variety of interpretations of "Probability," including Classical, Enumerative, Frequency, Formal, Metaphysical, Personal, Propensity, Chance and Logical conceptions of Probability, which we review and compare. We distinguish between "groupist" and "individualist" understandings of Probability, and explore both "group to individual" (G2i) and "individual to group" (i2G) approaches to characterising Individual Risk. Although in the end that concept remains subtle and elusive, some pragmatic suggestions for progress are made.

To structure, or not to structure?

March 2004


66 Reads

Some accounts of mental content represent the objects of beliefas structured, using entities that formally resemble the sentencesused to express and report attitudes in natural language; others adopta relatively unstructured approach, typically using sets or functions. Currently popular variants of the latter include classical andneoclassical propositionalism, which represent belief contents as setsof possible worlds and sets of centered possible worlds, respectively;and property self-ascriptionism, which employs sets of possibleindividuals. I argue against their contemporary proponents that allthree views are ineluctably plagued by generation gaps: they eitherovergenerate beliefs, undergenerate them, or both.

Duhem and the origins of statics: Ramifications of the crisis of 1903–04

January 1990


19 Reads

Much speculation on the sources of Duhem's historical interests fails to account for the major shifts in these interests: neither his belief in the continuous development of physics nor his Catholicism, when his Church was encouraging the study of generally Aristotelian scholastic thought, led to any interest in mediaeval science before 1904. Equally, his own claim that he was merely testing his views on the nature of physical theory is easily squared only with earlier work with no trace of mediaeval science. Behind this discontinuity lies a major crisis. Though not a positivist, Duhem had based all his work on assumptions acceptable to positivists. One of these, the sterility of the Middle Ages, was refuted by his chance discovery of evidence of genuine mediaeval science in the autumn of 1903, but that left the doctrine of scholastic sterility intact.

Apperception and the 1787 transcendental deduction

June 1981


10 Reads

This paper concerns the problem of how Kant can validate a questionable claim that he makes in §16 of the 1787 B-edition of the Transcendental Deduction of the Categories, as well as the relation of that claim to Kant's account of apperception, or the intellectual consciousness of self. 1 The paper has four parts. In the first, I sketch the Transcendental Deduction and show how the problem of validating the claim in question arises. The second part then indicates three solutions to this problem which Kant does or could offer and ultimately rejects all of them. The third solution, however, is seen at least to commit Kant to assertions like those which he makes in the Deduction and Paralogisms about apperception. So one might hope to support this solution by appeal to Kant's general views on apperception. However, in the third part of the paper I suggest the hypothesis that those views, insofar as they bear on our particular problem of validation, can be regarded as the product of a conflation by Kant of the traditional view of self-awareness with his 'revisionary' view of knowledge first offered in the first Critique. If this hypothesis is plausible, it appears that Kant's general views on apperception can scarcely lend any satisfactory support to our third solution to the validation problem in the Deduction. It also seems possible that various insights into the nature of self or of self-awareness that Strawson and others have attributed to the relevant part of Kant's work are only consequences of the confiation in question. In the fourth part of the paper I therefore conclude that though the problem with which we have been dealing leads us to a sharper understanding of Kant's account of apperception than has been previously available, the problem cannot be solved within Kant's framework in the way in which we would like. So measures to circumvent it must be adopted by students of the Transcendental Deduction. Before turning to the Deduction itself, let me note that this paper is not meant to provide a full-scale discussion of all of Kant's views on apperception. Rather, I have deliberately restricted attention to those

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