•  360
    Physical hypercomputation and the church–turing thesis
    with Itamar Pitowsky
    Minds and Machines 13 (1): 87-101. 2003.
    We describe a possible physical device that computes a function that cannot be computed by a Turing machine. The device is physical in the sense that it is compatible with General Relativity. We discuss some objections, focusing on those which deny that the device is either a computer or computes a function that is not Turing computable. Finally, we argue that the existence of the device does not refute the Church–Turing thesis, but nevertheless may be a counterexample to Gandy's thesis.
  •  292
    More on Global Supervenience
    Philosophy and Phenomenological Research 59 (3): 691-701. 1999.
    Jaegwon Kim contends that global supervenience is consistent with non-materialistic cases. Paull and Sider, Horgan, as well as Kim, attempt to defend it from these charges. It is shown here that their defense is only partially successful. Their defense meets one challenge to global supervenience---the hydrogen-atom case---but fails to meet other, ‘local’, cases. It is suggested that the other challenges can be met if global supervenience is combined with weak supervenience. The combination of gl…Read more
  •  213
    Are all three of Marr's levels needed? Should they be kept distinct? We argue for the distinct contributions and methodologies of each level of analysis. It is important to maintain them because they provide three different perspectives required to understand mechanisms, especially information-processing mechanisms. The computational perspective provides an understanding of how a mechanism functions in broader environments that determines the computations it needs to perform. The representation …Read more
  •  212
    Why we view the brain as a computer
    Synthese 153 (3): 393-416. 2006.
    The view that the brain is a sort of computer has functioned as a theoretical guideline both in cognitive science and, more recently, in neuroscience. But since we can view every physical system as a computer, it has been less than clear what this view amounts to. By considering in some detail a seminal study in computational neuroscience, I first suggest that neuroscientists invoke the computational outlook to explain regularities that are formulated in terms of the information content of elect…Read more
  •  210
    Structural Representations and the Brain
    British Journal for the Philosophy of Science 63 (3): 519-545. 2012.
    In Representation Reconsidered , William Ramsey suggests that the notion of structural representation is posited by classical theories of cognition, but not by the ‘newer accounts’ (e.g. connectionist modeling). I challenge the assertion about the newer accounts. I argue that the newer accounts also posit structural representations; in fact, the notion plays a key theoretical role in the current computational approaches in cognitive neuroscience. The argument rests on a close examination of comp…Read more
  •  177
    Physical Computation: How General are Gandy’s Principles for Mechanisms?
    with B. Jack Copeland
    Minds and Machines 17 (2): 217-231. 2007.
    What are the limits of physical computation? In his ‘Church’s Thesis and Principles for Mechanisms’, Turing’s student Robin Gandy proved that any machine satisfying four idealised physical ‘principles’ is equivalent to some Turing machine. Gandy’s four principles in effect define a class of computing machines (‘Gandy machines’). Our question is: What is the relationship of this class to the class of all (ideal) physical computing machines? Gandy himself suggests that the relationship is identity…Read more
  •  158
    Do Accelerating Turing Machines Compute the Uncomputable?
    with B. Jack Copeland
    Minds and Machines 21 (2): 221-239. 2011.
    Accelerating Turing machines have attracted much attention in the last decade or so. They have been described as “the work-horse of hypercomputation” (Potgieter and Rosinger 2010: 853). But do they really compute beyond the “Turing limit”—e.g., compute the halting function? We argue that the answer depends on what you mean by an accelerating Turing machine, on what you mean by computation, and even on what you mean by a Turing machine. We show first that in the current literature the term “accel…Read more
  •  149
    Content, computation and externalism
    Mind 110 (438): 369-400. 2001.
    The paper presents an extended argument for the claim that mental content impacts the computational individuation of a cognitive system (section 2). The argument starts with the observation that a cognitive system may simultaneously implement a variety of different syntactic structures, but that the computational identity of a cognitive system is given by only one of these implemented syntactic structures. It is then asked what are the features that determine which of implemented syntactic struc…Read more
  •  133
    Marr on computational-level theories
    Philosophy of Science 77 (4): 477-500. 2010.
    According to Marr, a computational-level theory consists of two elements, the what and the why . This article highlights the distinct role of the Why element in the computational analysis of vision. Three theses are advanced: ( a ) that the Why element plays an explanatory role in computational-level theories, ( b ) that its goal is to explain why the computed function (specified by the What element) is appropriate for a given visual task, and ( c ) that the explanation consists in showing that …Read more
  •  129
    Two dogmas of computationalism
    Minds and Machines 7 (3): 321-44. 1997.
      This paper challenges two orthodox theses: (a) that computational processes must be algorithmic; and (b) that all computed functions must be Turing-computable. Section 2 advances the claim that the works in computability theory, including Turing's analysis of the effective computable functions, do not substantiate the two theses. It is then shown (Section 3) that we can describe a system that computes a number-theoretic function which is not Turing-computable. The argument against the first th…Read more
  •  117
    Global Supervenience, Coincident Entities and Anti-Individualism
    Philosophical Studies 109 (2): 171-196. 2002.
    Theodore Sider distinguishes two notions of global supervenience: strong global supervenience and weak global supervenience. He then discusses some applications to general metaphysical questions. Most interestingly, Sider employs the weak notion in order to undermine a familiar argument against coincident distinct entities. In what follows, I reexamine the two notions and distinguish them from a third, intermediate, notion (intermediate global supervenience). I argue that (a) weak global superve…Read more
  •  109
    Strong Global Supervenience is Valuable
    Erkenntnis 71 (3): 417-423. 2009.
    It is generally assumed that everything that can be said about dependence with the notion of strong global supervenience can also be said with the notion of strong supervenience. It is argued here, however, that strong global supervenience has a metaphysically distinctive role to play. It is shown that when the relevant sets include relations , strong global supervenience and strong supervenience are distinct. It is then concluded that there are claims about dependence of relations that can be m…Read more
  •  106
    Anomalism and supervenience: A critical survey
    Canadian Journal of Philosophy 39 (2). 2009.
    The thesis that mental properties are dependent, or supervenient, on physical properties, but this dependence is not lawlike, has been influential in contemporary philosophy of mind. It is put forward explicitly in Donald Davidson's seminal ‘Mental Events.’ On the one hand, Davidson claims that the mental is anomalous, that ‘there are no strict deterministic laws on the basis of which mental events can be predicted and explained’, and, in particular, that there are no strict psychophysical laws.…Read more
  •  106
    The paper criticizes standard functionalist arguments for multiple realization. It focuses on arguments in which psychological states are conceived as computational, which is precisely where the multiple realization doctrine has seemed the strongest. It is argued that a type-type identity thesis between computational states and physical states is no less plausible than a multiple realization thesis. The paper also presents, more tentatively, positive arguments for a picture of local reduction.
  •  100
    Computation, Implementation, Cognition
    Minds and Machines 22 (2): 137-148. 2012.
    Putnam (Representations and reality. MIT Press, Cambridge, 1988) and Searle (The rediscovery of the mind. MIT Press, Cambridge, 1992) famously argue that almost every physical system implements every finite computation. This universal implementation claim, if correct, puts at the risk of triviality certain functional and computational views of the mind. Several authors have offered theories of implementation that allegedly avoid the pitfalls of universal implementation. My aim in this paper is t…Read more
  •  98
    Concepts of Supervenience Revisited
    Erkenntnis 78 (2): 469-485. 2013.
    Over the last 3 decades a vast literature has been dedicated to supervenience. Much of it has focused on the analysis of different concepts of supervenience and their philosophical consequences. This paper has two objectives. One is to provide a short, up-do-date, guide to the formal relations between the different concepts of supervenience. The other is to reassess the extent to which these concepts can establish metaphysical theses, especially about dependence. The conclusion is that strong gl…Read more
  •  96
    It is generally accepted that, in the cognitive and neural sciences, there are both computational and mechanistic explanations. We ask how computational explanations can integrate into the mechanistic hierarchy. The problem stems from the fact that implementation and mechanistic relations have different forms. The implementation relation, from the states of an abstract computational system to the physical, implementing states is a homomorphism mapping relation. The mechanistic relation, however,…Read more
  •  92
    Effective Computation by Humans and Machines
    Minds and Machines 12 (2): 221-240. 2002.
    There is an intensive discussion nowadays about the meaning of effective computability, with implications to the status and provability of the Church–Turing Thesis (CTT). I begin by reviewing what has become the dominant account of the way Turing and Church viewed, in 1936, effective computability. According to this account, to which I refer as the Gandy–Sieg account, Turing and Church aimed to characterize the functions that can be computed by a human computer. In addition, Turing provided a hi…Read more
  •  91
    What is computer science about?
    The Monist 82 (1): 131-149. 1999.
    What is computer-science about? CS is obviously the science of computers. But what exactly are computers? We know that there are physical computers, and, perhaps, also abstract computers. Let us limit the discussion here to physical entities and ask: What are physical computers? What does it mean for a physical entity to be a computer? The answer, it seems, is that physical computers are physical dynamical systems that implement formal entities such as Turing-machines. I do not think that this a…Read more
  •  86
    Brains as analog-model computers
    Studies in History and Philosophy of Science Part A 41 (3): 271-279. 2010.
    Computational neuroscientists not only employ computer models and simulations in studying brain functions. They also view the modeled nervous system itself as computing. What does it mean to say that the brain computes? And what is the utility of the ‘brain-as-computer’ assumption in studying brain functions? In previous work, I have argued that a structural conception of computation is not adequate to address these questions. Here I outline an alternative conception of computation, which I call…Read more
  •  85
    In defense of the semantic view of computation
    Synthese 197 (9): 4083-4108. 2020.
    The semantic view of computation is the claim that semantic properties play an essential role in the individuation of physical computing systems such as laptops and brains. The main argument for the semantic view rests on the fact that some physical systems simultaneously implement different automata at the same time, in the same space, and even in the very same physical properties. Recently, several authors have challenged this argument. They accept the premise of simultaneous implementation bu…Read more
  •  68
    Supervenience and Anomalism are Compatible
    Dialectica 65 (2): 241-266. 2011.
    I explore a Davidsonian proposal for the reconciliation of two theses. One is the supervenience of the mental on the physical, the other is the anomalism of the mental. The gist of the proposal is that supervenience and anomalism are theses about interpretation. Starting with supervenience, the claim is that it should not be understood in terms of deeper metaphysical relations, but as a constraint on the relations between the applications of physical and mental predicates. Regarding anomalism, t…Read more
  •  62
    Computation, San Diego Style
    Philosophy of Science 77 (5): 862-874. 2010.
    What does it mean to say that a physical system computes or, specifically, to say that the nervous system computes? One answer, endorsed here, is that computing is a sort of modeling. I trace this line of answer in the conceptual and philosophical work conducted over the last 3 decades by researchers associated with the University of California, San Diego. The linkage between their work and the modeling notion is no coincidence: the modeling notion aims to account for the computational approach …Read more
  •  52
    A key component of scientific inquiry, especially inquiry devoted to developing mechanistic explanations, is delineating the phenomenon to be explained. The task of delineating phenomena, however, has not been sufficiently analyzed, even by the new mechanistic philosophers of science. We contend that Marr’s characterization of what he called the computational level provides a valuable resource for understanding what is involved in delineating phenomena. Unfortunately, the distinctive feature of …Read more
  •  46
    GOdel on Turing on Computability
    In A. Olszewski, J. Wole'nski & R. Janusz (eds.), Church's Thesis After Seventy Years, Ontos Verlag. pp. 1--393. 2006.
  •  44
    Computational physical systems may exhibit indeterminacy of computation (IC). Their identified physical dynamics may not suffice to select a unique computational profile. We consider this phenomenon from the point of view of cognitive science and examine how computational profiles of cognitive systems are identified and justified in practice, in the light of IC. To that end, we look at the literature on the underdetermination of theory by evidence and argue that the same devices that can be succ…Read more
  •  38
    The Brain as an Input–Output Model of the World
    Minds and Machines 28 (1): 53-75. 2018.
    An underlying assumption in computational approaches in cognitive and brain sciences is that the nervous system is an input–output model of the world: Its input–output functions mirror certain relations in the target domains. I argue that the input–output modelling assumption plays distinct methodological and explanatory roles. Methodologically, input–output modelling serves to discover the computed function from environmental cues. Explanatorily, input–output modelling serves to account for the…Read more
  •  33
    1. Marr on Computational-Level Theories Marr on Computational-Level Theories (pp. 477-500)
    with John D. Norton, Holger Andreas, Jouni-Matti Kuukkanen, Aris Spanos, Eckhart Arnold, Elliott Sober, Peter Gildenhuys, and Adela Helena Roszkowski
    Philosophy of Science 77 (4): 477-500. 2010.
    According to Marr, a computational-level theory consists of two elements, the what and the why. This article highlights the distinct role of the Why element in the computational analysis of vision. Three theses are advanced: that the Why element plays an explanatory role in computational-level theories, that its goal is to explain why the computed function is appropriate for a given visual task, and that the explanation consists in showing that the functional relations between the representing c…Read more