The empirical study of visual space has centered on determining its geometry, whether it is a perspective projection, flat or curved, Euclidean or non-Euclidean, whereas the topology of space consists of those properties that remain invariant under stretching but not tearing. For that reason distance is a property not preserved in topological space whereas the property of spatial order is preserved. Specifically the topological properties of dimensionality, orientability, continuity, and connectivity define “real” space as studied by physics and are the (...) spatial properties that characterize the physical universe as being an integral whole. By contrast the geometrical analysis of VS has taken little cognizance of its topology. Instead such properties have been presupposed a priori rather than being established a posteriori by empirical means, perhaps because these properties are self-evident. Applying the method of coordinative definition expounded by Hans Reichenbach for determining geometrical and topological properties of physical space, it can be shown that VS fulfills the topological criteria of being a “real” space sui generis. Though theorized to be produced by the brain, the topology of VS is not topologically equivalent with the structure and activity of the brain because, as will be shown, the topology of VS cannot be formed from the topology of the brain without tearing and/or cutting and pasting. (shrink)

According to Reid, color sensations are not extended nor are they arranged in figured patterns. Reid further claimed that ‘there is no sensation appropriated to visible figure.’ Reid justified these controversial claims by appeal to Cheselden's report of the experiences of a young man affected by severe cataracts, and by appeal to cases of perception of visible figure without color. While holding fast to the principle that sensations are not extended, Dugald Stewart tried to show that ‘a variety of colour (...) sensations is a necessary means for the perception of visible figure.’ According to John Fearn, two motives appear to be central to Reid's views about color sensations and extension: his commitment to the Cartesian doctrine of the immateriality of the soul, and his attempt to evade ‘Hume's dilemma’ about the existence and immateriality of the soul. (shrink)

The concept of simultaneous masking in visual field is discussed, in the light of classical examples, of the various kinds of the phenomenon, of a modal completion, of the figure/ground phenomenon, of ambiguous and reversible figures, of mimicry and camouflage and eventually of the complexity of the stimulus. There is some reference to masking in auditory field. The “reality” of the masked configuration is discussed, drawing the conclusion that it is perceptually unreal. The fact that the masking phenomenon cannot take (...) place without comparison between two perceptual acts – what we see at one moment and what we see a moment after LATER – and the fact that the masked configuration pops out with some surprise, lead to the conclusion that simultaneous masking in visual field is not a bare perceptual phenomenon, but a psychological process not unlike insight. (shrink)

The concept of empiricism evokes both a historical tradition and a set of philosophical theses. The theses are usually understood to have been developed by Locke, Berkeley, and Hume. But these figures did not use the term “empiricism,” and they did not see themselves as united by a shared epistemology into one school of thought. My dissertation analyzes the debate that elevated the concept of empiricism (and of an empiricist tradition) to prominence in English-language philosophy. -/- In the 1870s and (...) ’80s a lively debate about psychology emerged. Neo-Kantian idealists criticized the very idea that the mind can be studied scientifically. A group of philosopher-psychologists responded, often in Mind. They were among the first to call themselves “empiricists,” arguing that psychology could provide a scientific basis for philosophical progress. Idealists held that empirical psychology depended on premises developed by Locke, Berkeley, and Hume. These premises were allegedly absurd because they rendered ideas of extension, as well as other ideas crucial to natural science, unreal. Those who wanted to advance psychology towards becoming a legitimate science were forced to engage these philosophical attacks, while at the same time to develop empirical theories that could successfully explain some characteristics of experience. I show how James’s theory of space perception accomplished both tasks. -/- In developing this theory, James found he had to reject the Lockean notion that reality is associated with passively-registered sensations. James also abandoned Berkeley and Hume’s claim that ideas are ultimately derived from atomic sensations. Instead, James presented experimental evidence that sensation is a continuous stream. The mind must actively parse this stream if it is to gain a coherent representation of its environment. I argue that James’s stream-of-thought thesis served as a presupposition of his entire psychology. The thesis showed how the labor of investigating the mind could be divided between philosophers and scientists, and in a manner sensitive to the concerns of both. The stream thesis also provided a scientific basis for a new philosophical empiricism that, I argue, has a hidden legacy in the history of analytic philosophy. (shrink)

This review addresses the role of early sensory areas in the awareness of tactile information in humans. The results of recent studies dealing with this important topic are critically discussed: In particular, we report on evidence from neuropsychology, neurophysiology, neuroimaging, and behavioral experiments that have highlighted the crucial role played by the primary somatosensory cortex in mediating our awareness of tactile information. Phenomena, such as tactile hallucinations, tactile illusions, the perception of supernumerary limbs, and synaesthesia are also discussed. The research (...) reviewed here clearly shows that the activation of SI is necessary, but not sufficient, for the awareness of touch. On the basis of the evidence outlined here, we propose a neurocognitive model that provides a conceptual framework in which to interpret the results of the literature regarding tactile consciousness. (shrink)