The book provides a historical and systematic exposition of the semantic theory of truth formulated by Alfred Tarski in the 1930s. This theory became famous very soon and inspired logicians and philosophers. It has two different, but interconnected aspects: formal-logical and philosophical. The book deals with both, but it is intended mostly as a philosophical monograph. It explains Tarski’s motivation and presents discussions about his ideas as well as points out various applications of the semantic theory of truth to philosophical (...) problems. (shrink)

As the word “optics” was understood from antiquity into and beyond the early modern period, it did not mean simply the physics and geometry of light, but meant the “theory of vision” and included what we should now call physiological and psychological aspects. From antiquity, these aspects were subject to geometrical analysis. Accordingly, the geometry of visual experience has long been an object of investigation. This chapter examines accounts of size and distance perception in antiquity (Euclid and Ptolemy) and the (...) Middle Ages (Ibn al-Haytham), before turning to "natural geometry" in Kepler and Descartes. It finds a purely mechanical realization of natural geometry in Descartes (primarily in his L'Homme, 1664), in which he conceives states of the visual system as varying in accordance with distance, much as his geometrical compasses vary their spatial relations in accordance with geometrical proportions. This reading challenges the notion that a two-dimensional sensation (without three-dimensional phenomenality) was universally accepted prior to the nineteenth century by positing a direct psychophysiological account of the experience of distance in Descartes. It thereby challenges the interpretations of Descartes on natural geometry of George Berkeley, Nancy Maull, Margaret Wilson, Erwin Panofsky, and Jonathan Crary. (shrink)

The problem of philosophical skepticism relates to the difficulty involved in underwriting the claim that we know anything of spatio-temporal reality. It is often claimed, in fact, that proper philosophical scrutiny reveals quite the opposite from what common sense suggests. Knowledge of external reality is thought to be even quite obviously denied to us as a result of the alleged fact that we all fail to know that certain skeptical scenarios do not obtain. A skeptical scenario is one in which (...) we have neurological occurrences just like any normal situation in which we actually perceive spatio-temporal objects, but where we are deceived in some sense as a result of the manipulation of our brains from some outside source. In this work I attempt to address the problem of philosophical skepticism by claiming that most of us are able to come to know plenty about external reality, since we can come to realize that a certain philosophical theory of perception is correct. The theory I have in mind is what I call a non-cognitive theory of perception. According to this view, perceptual experience is defined by continuous, sensitive behavioral interaction with spatio-temporal objects of the appropriate size, shape, hardness, speed, etc. Knowing that this theory of perception is correct is equivalent to knowing that we know plenty about external reality. This is ultimately because by knowing that a non-cognitive theory of perception is true, we know that any skeptical scenario must fail to obtain. The structure of the work proceeds by first discussing the significance of the problem of philosophical skepticism in some detail. Chapter 1 lays out how the problem does indeed forcefully arise if it is conceded that we fail to know that the skeptical scenarios fail to obtain. Chapter 2 develops the sort of view of our epistemological situation that falls out of accepting without qualification that the problem exists. Chapter 3 examines and criticizes certain popular responses to the skeptical problem. The main goal of these first three preliminary chapters is to indicate that once it is admitted that we fail to know that the skeptical scenarios fail to obtain, the problem of philosophical skepticism forcefully presents itself. Chapter 4, however, attacks the idea that we fail to know that the skeptical scenarios fail to obtain. In this chapter I argue that this idea is wedded to the position that a certain theory of perception is correct. The theory in question is what I call a conjunctive theory of veridical experience. According to this view, normal experience of spatio-temporal objects occurs when a subject has a certain perceptual experience, and that experience also happens to match up with and/or be satisfied by what is really the case. Only when a theory of this sort is assumed, I argue, is the claim that we fail to know that the skeptical scenarios fail to obtain found to be obvious. In chapter 5 I argue that, in fact, a non-cognitive theory, rather than a conjunctive theory, is the correct view to maintain. In the final chapter 6 I develop the epistemological position that falls out of accepting a non-cognitive theory. (shrink)

Descartes maintained that sensations of color and the like misrepresent the material world in normal circumstances. Some prominent scholars have argued that, to explain this Cartesian view, we must attribute to Descartes a causal account of sensory representation. I contend that neither the arguments motivating this reading nor the textual evidence offered in its support is sufficient to justify such attribution. Both textual and theoretical reasons point in the direction of an (at least partial) internalist account of Descartes' views on (...) sensory representation. (shrink)

According to Kepler and Descartes, the geometry of the triangle formed by the two eyes when focused on a single point affords perception of the distance to that point. Kepler characterized the processes involved as associative learning. Descartes described the processes as a “ natural geometry.” Many interpreters have Descartes holding that perceivers calculate the distance to the focal point using angle-side-angle, calculations that are reduced to unnoticed mental habits in adult vision. This article offers a purely psychophysiological interpretation of (...) Descartes’s natural geometry. In his account of perceived limb position from the Treatise on Man, he envisioned a central brain state that controls ocular convergence and thereby co-varies with the distance from observer to object. A psychophysiological law relates the visual perception of distance to this brain state. Descartes also invokes more traditional theories of distance and size perception based on unnoticed judgments, yielding a hybrid account. (shrink)

In his recent survey of the “dialectic of creation” in seventeenth-century philosophy, Thomas Lennon has suggested that Descartes’s assumptions about causality encourage a kind of “pantheistic emanationism”. Lennon notes that Descartes regularly invokes the principle that there is nothing in the effect which was not previously present, either formally or eminently, in the cause. Descartes also believes that God is the continuous, total, and efficient cause of everything. From these assumptions it should follow that everything that exists in the created (...) world is previously present in God. Indeed, Descartes embraces the emanationist doctrine explicitly when, at the end of his replies to the Second Set of Objections, he arranges the arguments of the Meditations in “geometrical fashion.” The demonstration of Proposition III includes a sub-proof of the proposition that “he who preserves me has within himself, either formally or eminently, whatever is in me”. Since God preserves the entire universe, it follows that everything is in him, either formally or eminently. While far from the radical Spinozistic view that God and the world are identical, the notion that everything in creation is also in God would seem to have its own unwelcome theological consequences, at least from a Cartesian point of view. In particular, it implies that extension, and hence divisibility, are in God. But, as Descartes himself cautions, “being divisible is an imperfection” and so completely foreign to God. (shrink)

In the Fifth Meditation Descartes considers the problem of knowledge preservation : the challenge of accounting for the diachronic certainty of perfect knowledge [scientia]. There are two general solutions to PKP in the literature: the regeneration solution and the infallible memory solution. While both readings pick up on features of Descartes’ considered view, I argue that they ultimately fall short. Salvaging pieces from both readings and drawing from Descartes’ virtue theory, I argue on textual and systematic grounds for a dispositionalist (...) solution. On this view, the diachronic certainty of scientia is achieved through virtuous habits of belief. (shrink)

The aim of this thesis is to investigate the role that the imagination plays in the later philosophy of René Descartes. The thesis will look at two related questions: the status of the imagination as a mode of thought dependent on the body; the role of the imagination in object-perception. Throughout, the traditional view of Descartes as a Cartesian Dualist is rejected and a more holistic approach is taken towards the relationship between mind and body, in which Descartes’ claims that (...) the two make up a “substantial union” are taken seriously. Part One deals with the relationship between mind and body. I argue that Cartesian Dualism cannot account for the faculties of sensation and imagination, because they have a corporeal basis. However, the ‘union of mind and body’, Descartes’ device for explaining their interaction, can. I end Part One by identifying a problem with the paradigm case of mind-body interaction, object-perception. To determine the object of an idea there needs to be a mechanism to marry the two ingredients of perception: the innate ideas of geometry in the intellect, and ‘adventitious’ ideas of the object delivered by the senses. Otherwise we have no explanation for how the essentially ‘inward-looking’ intellect can apply its ideas to the essentially passive sensations. Part Two focuses on the imagination and the question of object-perception raised in Part One. I argue against the largely-held view in the secondary literature that, with the advent of the cogito, the imagination’s cognitive profile declined sharply. I argue that, in fact, the corporeal basis of the imagination places it beautifully to bridge the gap in object-perception, and that this is part of its role in all Descartes’ discussions on the topic. The other, related, role of the imagination is to conjure fictions and hypotheses, suiting it for scientific and epistemological endeavours. The fact that the imagination is not tied to what is present to the senses, even though it receives its original content from them, means that it can manipulate ideas of corporeal things; including the innate notions of extension, shape and motion so key to gaining a clear and distinct idea of matter. (shrink)

There were two prevailing sentiments in Europe after the Reformation: One opposing papal authority and one advocating individual freedom. This paper analyzes these two sentiments and finds that the concept of conscience is crucial in understanding them. The issue of conscience is about judging truth and good, and in initiating the Reformation, Martin Luther heavily appealed to his conscience while countering Catholic attacks. With the wide dispersal of the Reformation, Luther’s notion of conscience was well received among his supporters throughout (...) Europe. Descartes later transformed Luther’s conscience into an epistemological being (the cogito ), and argued that its existence was the only valid thing that survived his thorough skepticism — and as such is the foundation of human knowledge. Rousseau continued this line of thinking, which we call subjectivism, and re-employed the term conscience as a replacement for cogito , holding that conscience is the final authority in judging good and bad; that, as the starting point of human existence, it cannot be withheld from any human being; and that it therefore constitutes an inalienable human right. This paper argues that the Enlightenment was a subjectivist movement propelled by this conscience- cogito -conscience conceptualization, and that it sought to enlighten this inalienable conscience. (shrink)

Two major interpretations have been advanced for the sum res cogitans passage in Descartes’s Second Meditation. According to the first interpretation, he argues in this passage that only thinking belongs to his essence. According to the second interpretation, due to Anthony Kenny, Harry Frankfurt and others, no such claim is defended by Descartes. Rather, it is his aim to argue that only thinking can be ascribed to him with certainty. In this essay, it will be shown that the “naive”, essentialist (...) reading of the sum res cogitans reasoning is closer to the text than the perhaps more sophisticated, purely epistemic reading. Although the interpretation defended here is not new, it will be arrived at by way of new arguments. (shrink)