check
Publications | Oron Shagrir

Publications

2010
Oron Shagrir. 2010. Marr On Computational-Level Theories. Philosophy Of Science, 77, 4, Pp. 477–500. doi:10.1086/656005. Abstract
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 the functional relations between the representing cells are similar to the "external" mathematical relations between the entities that these cells represent.
2009
Oron Shagrir. 2009. Anomalism And Supervenience: A Critical Survey. Canadian Journal Of Philosophy, 39, 2, Pp. 237–272. doi:10.1353/cjp.0.0047.
Oron Shagrir. 2009. Strong Global Supervenience Is Valuable. Erkenntnis, 71, 3, Pp. 417–423. doi:10.1007/s10670-009-9187-5. Abstract
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 made with the global notion of strong supervenience but not with the "local" (individual) one.
2007
B. Jack Copeland and Shagrir, Oron . 2007. Physical Computation: How General Are Gandy's Principles For Mechanisms?. Minds And Machines, 17, 2, Pp. 217–231. doi:10.1007/s11023-007-9058-2. Abstract
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. We do not share this view. We will point to interesting examples of (ideal) physical machines that fall outside the class of Gandy machines and compute functions that are not Turing-machine computable.
2006
Oron Shagrir. 2006. Why We View The Brain As A Computer. Synthese, 153, 3, Pp. 393–416. doi:10.1007/s11229-006-9099-8. Abstract
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 electrical signals. I then indicate why computational theories have explanatory force with respect to these regularities:in a nutshell, they underscore correspondence relations between formal/mathematical properties of the electrical signals and formal/mathematical properties of the represented objects. I finally link my proposal to the philosophical thesis that content plays an essential role in computational taxonomy.
2004
Oron Shagrir. 2004. Super-Tasks, Accelerating Turing Machines And Uncomputability. Theoretical Computer Science, 317, 1-3, Pp. 105–114. doi:10.1016/j.tcs.2003.12.007. Abstract
Accelerating Turing machines are devices with the same computational structure as Turing machines (TM), but able to perform super-tasks. We ask whether performing super-tasks alone produces more computational power; for example, whether accelerating TM can solve the halting problem. We conclude that this is not the case. No accelerating TM solves the halting problem. The argument rests on an analysis of the reasoning that leads to Thomson's paradox. The key point is that the paradox rests on a conflation of different perspectives of accelerating processes. This leads to concluding that the same conflation underlies the claim that accelerating TM can solve the halting problem.
2003
Oron Shagrir and Pitowsky, Itamar . 2003. Physical Hypercomputation And The Church-Turing Thesis. Minds And Machines, 13, 1, Pp. 87–101. doi:10.1023/A:1021365222692. Abstract
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.
2002
Oron Shagrir. 2002. Effective Computation By Humans And Machines. Minds And Machines, 12, 2, Pp. 221–240. doi:10.1023/A:1015694932257. Abstract
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 highly convincing argument for CTT by analyzing the processes carried out by a human computer. I then contend that if the Gancy-Sieg account is correct, then the notion of effective computability has changed after 1936. Today computer scientists view effective computability in terms of finite machine computation. My contention is supported by the current formulations of CTT, which always refer to machine computation, and by the current argumentation for CTT, which is different from the main arguments advanced by Turing and Church. I finally turn to discuss Robin Gandy's characterization of machine computation. I suggest that there is an ambiguity regarding the types of machines Gandy was postulating. I offer three interpretations, which differ in their scope and limitations, and conclude that none provides the basis for claiming that Gandy characterized finite machine computation.
Oron Shagrir. 2002. Global Supervenience, Coincident Entities And Anti-Individualism. Philosophical Studies, 109, 2, Pp. 171–196. doi:10.1023/A:1016224703009. Abstract
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 supervenience is not an adequate notion of dependence; (b) weak global supervenience does not capture certain assumptions about coincidence relations; (c) these assumptions are better accommodated by the stronger notion of intermediate global supervenience; (d) intermediate global supervenience, however, is also not an adequate notion of dependence; and (e) strong global supervenience is an adequate notion of dependence. It also fits in with anti-individualism about the mental. It does not, however, serve to rebut arguments against coincident entities.
2001
Oron Shagrir. 2001. Content, Computation And Externalism. Mind, 110, 438, Pp. 369–400. doi:10.1093/mind/110.438.369. Abstract
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 structures is the computational structure of the system, and it is contended that these features are certain aspects of mental content. The argument helps (section 3) to reassess the thesis known as computational externalism, namely, the thesis that computational theories of cognition make essential reference to features in the individual's environment. It is suggested that the familiar arguments for computational externalism - which rest on thought experiments and on exegesis of Marr's theories of vision - are unconvincing, but that they can be improved. A reconstruction of the visexaudex thought experiment is offered in section 3.1. An outline of a novel interpretation of Marr's theories of vision is presented in section 3.2. The corrected arguments support the claim that computational theories of cognition are intentional. Computational externalism is still pending, however, upon the thesis that psychological content is extrinsic.
1999
Oron Shagrir. 1999. More On Global Supervenience, 59, 3, Pp. 691. doi:10.2307/2653789. Publisher's Version
O Shagrir. 1999. What Is Computer Science About?. Monist, 82, 1, Pp. 131-149. doi:10.5840/monist19998214.
1998
Oron Shagrir. 1998. Multiple Realization, Computation And The Taxonomy Of Psychological States. Synthese, 114, 3, Pp. 445–461. doi:10.1023/A:1005072701509. Abstract
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.
1997
Oron Shagrir. 1997. Two Dogmas Of Computationalism. Minds And Machines, 7, 3, Pp. 321–344. doi:10.1023/A:1008236522699. Abstract
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 thesis proceeds in two stages. It is first shown (Section 4) that whether a process is algorithmic depends on the way we describe the process. It is then argued (Section 5) that systems compute even if their processes are not described as algorithmic. The paper concludes with a suggestion for a semantic approach to computation.
1995
Oron Shagrir. 1995. Review Of Goldman (1993): Readings In Philosophy And Cognitive Science, 3, 2, Pp. 377–385. doi:10.1075/pc.3.2.13sha. Publisher's Version
1992
B GLYMOUR, GRUSH, R, HARDCASTLE, VG , KEELEY, B, RAMSEY, J, Shagrir, O, and WATSON, E. 1992. The Cartesian Theater Stance. Behavioral And Brain Sciences, 15, 2, Pp. 209-210. doi:10.1017/S0140525X0006831X.
Oron Shagrir. 1992. A Neural Net With Self-Inhibiting Units For The N-Queens Problem, 03, 03, Pp. 249–252. doi:10.1142/s0129065792000206. Publisher's Version
1989
אורון שגריר. 1989. הגישה הקלאסית והגישה הקישורית במדעים הקוגניטיביים. עיון: רבעון פילוסופי, ל"ח, Pp. 265–286.