Augustine is commonly interpreted as endorsing an extramission theory of perception in De quantitate animae. A close examination of the text shows, instead, that he is committed to its rejection. I end with some remarks about what it takes for an account of perception to be an extramission theory and with a review of the strength of evidence for attributing the extramission the- ory to Augustine on the basis of his other works.

The paper presents a preliminary estimation of the extent of dissemination of optical texts, ideas, and issues among the masters connected with the Prague faculty of arts in the late 14th and early 15th century. Investigation of this topic, so far rather neglected, is based chiefly on manuscript research. The paper brings evidence that perspectiva was taught in Prague at least since the 1370s. It suggests that investigation of Prague quodlibetal disputations (ca. 1390s – 1410s) and consideration of perspectivist authorities (...) employed in these texts can also shed some light on the issue. However, the paper is mainly devoted to the question on the mechanism of vision disputed by Bohemian arts master John of Borotín (Iohannes de Borotin, 1378 – after 1458) in the quodlibet organised by John Hus in 1411. It is suggested that the single extant exemplar of the question (preserved in the codex Prague, National Library, X.H.18) probably is Borotín’s autograph. The structure and sources of the question are analysed, with the conclusion being that Borotín proposes a compromise between intromission and extramission influenced by John Peckham’s Perspectiva communis. A critical edition of Borotín’s question is appended to the paper. / / / Please note this article is published with Brepols Publishers as a Gold Open Access article under a Creative Commons CC 4.0: BY-NC license. The article is also freely available on the website of Brepols Publishers under this same license. (shrink)

Is vision merely a state of the beholder’s sensory organ which can be explained as an immediate effect caused by external sensible objects? Or is it rather a successive process in which the observer actively scanning the surrounding environment plays a major part? These two general attitudes towards visual perception were both developed already by ancient thinkers. The former is embraced by natural philosophers (e.g., atomists and Aristotelians) and is often labelled “intromissionist”, based on their assumption that vision is an (...) outcome of the causal influence exerted by an external object upon a sensory organ receiving an entity from the object. The latter attitude to vision as a successive process is rather linked to the “extramissionist” theories of the proponents of geometrical optics (such as Euclid or Ptolemy) who suggest that an entity – a visual ray – is sent forth from the eyes to the object. The present paper focuses on the contributions to this ancient controversy proposed by some 13th-century Latin thinkers. [...]. (shrink)

My goal in this paper is to contribute to the literature on Roger Bacon's epistemology by focusing on the issue of perception of quantity. The reading I aim to substantiate is that Bacon's account is best understood in terms of indirect realism. I call it indirect realism because although we have access to quantities as they exist in nature, the account is mediated by the use of a quasi-syllogism. The quasi-syllogism is constructed based on three inputs, the species of the (...) eye, colour, and light. To defend this reading I follow five steps. First, I analyse the importance of quantity in perception, and then, in steps two and three, I look at Bacon's theory of perception from its two sides, extramission and intromission. In the fourth step I look at the quasi-syllogisms that mediate cognition of quantities, and in the fifth and final step, I draw all the threads together and make the case for Bacon's indirect realism of quantity perception. (shrink)

The sense of being stared at is the basis of evil eye beliefs, which are regarded as superstitions because the emission of any form of energy from the human eye has been rejected by Western science. However, brainwaves in the 1–40 Hertz, 1–10 microvolt range emitted through the eye can be detected using a high-impedance electrode housed inside electromagnetically insulated goggles. This signal, which the author calls “human ocular extramission,” is physiologically active and has distinct electrophysiological properties from simultaneous (...) brainwave recordings over the forehead. Western science's rejection of evil eye beliefs may be based on an erroneous rejection of a widespread component of human consciousness, the sense of being stared at, which may in turn be based on a real electrophysiological signal. The author proposes a series of future studies designed to determine whether human ocular extramission is the basis of evil eye beliefs. (shrink)

This paper is a commentary on Rupert Sheldrake’s analysis of theories of perception (in JCS, 2005, 2006). As Sheldrake points out in his fascinating review of ancient and modern thinking on this subject, theories of vision have ranged from “extramissive” theories that posit some active influence emanating from the eyes that both illuminates and influences the external world, “intramissive” theories that stress the influence of the external world on the (passive) brain, and theories in which intramissive and extramissive influences combine. (...) As Sheldrake notes, up to the 12th Century, extramissive theories were dominant, but with an increasing understanding of the way light reflected from an object is focused on the retina by the lens of the eye, intramissive theories have become dominant. Drawing on his research on staring experiments, Sheldrake defends an extramissive theory. In this commentary I argue for a model of perception that combines intramissive and extramissive influences, which accepts all third-person evidence for intramissive causal antecedents to visual perception while at the same time accepting the phenomenal evidence for the apparent external nature of the perceived world—an extramissive psychological effect that I refer to as “perceptual projection”. I also suggest some additions to the model that might begin to make sense of apparently extramissive causes of the type needed to explain staring experiments. Ultimately, I suggest, we may need to accept that we are in our minds, but might be partly out of our brains! -/- . (shrink)

[Sight Darting Forth from the Eyes: 13th-Century Franciscans and Augustine’s Authority in the Issue of Extramissionist Theory of Vision] One of the positions sometimes ascribed to Augustine is the so-called extramissionist conception of vision, i.e. the assumption that the sight is effectuated by something being sent out from the eyes, as opposed to more intuitive receptionist understanding of sight. The paper investigates the attitudes of eleven 13th-century Franciscan thinkers (from Alexander of Hales and John of La Rochelle in 1230s to (...) Roger Marston and Peter of England in 1280s) to this philosophical problem and Augustine’s authority in this issue. It is demonstrated that whereas the earliest generation of Franciscan thinkers does not conceptualise the issue at all, accepting rather Aristotelian receptionist account at face value, the later Franciscans (such as Roger Bacon) try to the reconcile both positions, which is, in turn, abandoned by the next generation (e.g., Peter of England). The unique example of paying tribute to Augustine without renouncing the philosophical scrutiny is Peter Olivi, who reformulates extramission into a more plausible account of the role of attention in the visual perception. (shrink)

In paragraphs 5 and 86 of the De sensibus Theophrastus gives a brief report of Plato’s views on the sense of vision and its object, i. e. colour, based on the Timaeus. Interestingly enough, he presents the Platonic doctrine as a third alternative to the extramission and intromission theories put forward by other ancient philosophers. In this article I examine whether or not Theophrastus’ account is impartial. I argue that at least some of his distortive departures from the Platonic (...) dialogue are due to his Aristotelian inheritance, even though they do not always represent Aristotle’s expressed views. (shrink)