In ?155 of his New Theory of Vision Berkeley explains that a hypothetical ?unbodied spirit? ?cannot comprehend the manner wherein geometers describe a right line or circle?.1The reason for this, Berkeley continues, is that ?the rule and compass with their use being things of which it is impossible he should have any notion.? This reference to geometrical tools has led virtually all commentators to conclude that at least one reason why the unbodied spirit cannot have knowledge of plane geometry is (...) because it cannot manipulate a ruler or a compass. In this article I will show that such an interpretation is flawed. I will instead argue that Berkeley's understanding of Euclidian geometry was based on Isaac Barrow's account of the foundations of geometry. On this view geometrical objects are conceived in terms of the idealized motion that generates the objects of geometry. Consequently, that what the unbodied spirit cannot do in this context is to form an idea of motion rather than being unable to handle geometrical tools. 1All references to Berkeley are from, A. A. Luce and T. E. Jessop (eds.), The Works of George Berkeley, Bishop of Cloyne (London: Thomas Nelson and Sons, Ltd., 1948) The following abbreviations are used: An Essay Towards A New Theory of Vision, section x = New Theory x; Philosophical Commentaries, entry x = Commentaries x; Part I of A Treatise concerning the Principles of Knowledge, section x = Principles x. All other references to Berkeley's works are of the form The Works of George Berkeley, Bishop of Cloyne, volume x, page y = Works, x, y. (shrink)

We attempt to clarify the nature of philosophic assertions about perception by considering how one can argue effectively against such assertions. Reasons are given, with illustrative assertions from Aristotle and Berkeley, why one cannot argue effectively against such either (1) by arguing for contrary assertions in competing theories or (2) by appealing to scientific observation. Effective arguments against such accounts include (1) those which demonstrate inconsistency within the account, (2) those which disclose an unintelligibility within the account, and (3) those (...) which show the account is inadequate in scope. These are illustrated respectively by arguments (i) against Phenomenalism, (ii) against Aristotle's account of the identity in act of sensing faculty and sensed object, and (iii) against Berkeley's account of observation through instruments. (shrink)

Berkeley desarrolla su teoría de la visión en la obra de juventud Ensayo para una nueva teoría de la visión, que por lo general ha sido leída atendiendo sólo a sus aspectos científicos o perceptuales. En este artículo propongo una lectura distinta, que busca mostrar que el Ensayo no sólo atiende aspectos científicos sino, por el contrario, anticipa el inmaterialismo de obras posteriores. Esto lo hace porque Dios cumple un importante papel en él, lo cual se debe, entre otras cosas, (...) a que la teoría de la visión es desarrollada en función de Dios, pues de Él depende tanto la vista y los objetos visibles como el argumento del lenguaje visual. (shrink)

At the beginning of the 18th century, Berkeley believed an anomaly pointed out by Isaac Barrow could be regarded as important evidence against the optical theories that had been established and standardized thanks to the works of Kepler and Newton. In this article, we want to show that Berkeley’s treatment of the Barrovian Case does not falsify these theories. We will contend that the strategy used by Berkeley to resolve the anomaly by alluding to a change of convention is a (...) strategy that the classical theorist could use as well. In other words, the classical theorist could also appeal to a change of convention to deal with the problem. (shrink)

There are two related points at which J.J. Gibson’s ecological theory of visual perception remains remarkably underspecified: Firstly, the notion of information for perception is not explicated in much detail beyond the claim that it “specifies” the environment for perception, and, thus being an objective affair, enables an organism to perceive action possibilities or “affordances.” Secondly, misperceptions of affordances and perceptual illusions are not clearly distinguished from each other. Although the first claim seems to suggest that any perceptual illusion amounts (...) to the misperception of affordances, there might be some relevant differences between various ways of getting things wrong. In this essay, Gibson’s notion of “specifying” information shall be reconstructed along the lines of Fred Dretske’s relational theory of information. This refined notion of information for perception will then be used to carve out the distinction between perceptual illusions and the misperception of affordances, with some help from the “Empirical Strategy” (developed by Purves et al.). It will be maintained that there are cases where perceptual illusions actually help an organism to correctly perceive an affordance. In such cases, the prima facie misrendered informational relations involved are kept intact by a set of appropriate transformation rules. Two of Gibson’s intuitions shall thus be preserved: the objectivity of informational relations and the empowerment of the organism as an active perceiver who uses those objective relations to his specific ends. (shrink)

Ein Homunkulus im philosophischen Sprachgebrauch ist eine postulierte menschenähnliche Instanz, die ausdrücklich oder unausdrücklich zur Erklärung der Arbeitsweise des menschlichen Geistes herangezogen wird. Als Homunkulus-Fehlschluß wird die Praxis bezeichnet, Prädikate, die auf kognitive oder perzeptive Leistungen einer ganzen Person zutreffen, auch auf Teile von Personen oder auf subpersonale Vorgänge anzuwenden, was typischerweise zu einem Regreß führt. Der vorliegende Beitrag erörtert den Homunkulus-Fehlschluß zunächst in argumentationstheoretischer Hinsicht und stellt dabei ein Diagnoseschema auf. Dann werden zwei Anwendungsfelder erörtert: Instanzenmodelle der Psyche (Platon, (...) Freud) sind ihrer Natur nach homunkulusgefährdet, denn es ist aufgrund der holistischen Zuschreibungsbedingungen mentaler Fähigkeiten schwer plausibel zu machen, wie eine innerpsychische Instanz den ihr zugedachten Beitrag leisten soll, ohne über eine eigene Psyche zu verfügen. Der zweite Anwendungsfall ist das Problem des invertierten Netzhautbildes in der Philosophie der Wahrnehmung, das wissenschafts- und philosophiegeschichtlich eingebettet und unter besonderer Berücksichtigung von Descartes diskutiert wird. Schließlich werden offensive Rechtfertigungen homunkularer Redeweisen erörtert und größtenteils zurückgewiesen. (shrink)