Mental Activity in Descartes’ Causal Theory of Sensory Perception

The aim of this paper is to to defend a reading of Descartes’ theory of sensory perception in which, as opposed to a widespread interpretation, the mind is not a passive receiver of inputs from the environment, but an active decoder of neural information that contributes to the propositional content of ideas. Given his mechanistic conception of matter, Descartes developed detailed physiological descriptions of the interaction between external objects and the brain. He envisaged this as an isomorphic relation in which the qualities of objects are explained in terms of geometrically derived properties (shape, size, position, and motion of micro-corpuscles). This process is often read as as culminating with the mind being passively ‘affected’ by the corporeal isomorph. Certainly, Descartes’ descriptions are often ambiguous, but the reading of mental passivity remains inadequate.

I argue for this interpretation through three claims. First, Descartes is concerned about a refined version of the mind-body problem that is not equivalent to the problem of interaction. It is rather a problem of dissimilarity between mental representations and mechanistic explanations that, interestingly, reflects a worry that is very much alive in contemporary philosophy of mind. The question is how the qualitative character of sensory experiences can arise from the categories of physical science. Second, Descartes’ account of brain-mind interaction accommodates a metaphysically interesting distinction between types of causes. This is supported by a textual fact that has been overlooked in the literature. Namely, that Descartes constructed a narrative that avoids expressions suggesting actual contact between brain and mind, while capturing a different type of cause that operates in an equally law-like manner. His choice of words for describing interaction might seem erratic but, in fact, it persistently reveals a delicate balance between the dismissal of efficient causation and the evoking of genuine causal powers.

Third, in the light of this exegesis, it is possible to reconstruct a causal story for brain-mind interaction along the lines of a semantic model based on Descartes’ identification of neural events with ‘natural signs’. In a semantic model, the mind becomes an active interpreter of isomorphs by producing meaningful outcomes in the form of ideas. Natural signs have been often interpreted as a mere analogy in Descartes’ theory, but I suggest that, on the contrary, the introduction of natural signs is the closest that Descartes got to fleshing out the workings of interaction. It is consonant with his terminology and it reveals mental activity as a necessary feature for the intelligibility of perceptual experience.

By reassessing Descartes’ views on mental activity, this interpretation presents a lucid description of perception that goes beyond the rigid rationalism that is credited to him. By taking a common description of dissimilarity between objects and ideas as a starting point, it explores an alternative, textually robust causal story for body-mind interaction, and it offers a different way of understanding the genesis of the notion of mental activity within the debate of sensory perception in Early Modern philosophy.

Descartes on Structural Representation without Resemblance: From Mathematics to Perception

Descartes was the first theorist of perception to realise that representation in perception need not be by means of resemblance between the representation and the thing represented, but that structural correspondence is sufficient for adequate representation. He elaborated on this in his Optics, and his physiology and theory of mind incorporate the idea. This constituted a revolution in our understanding of perception, and opened new paths both in physiology and in the philosophy of mind.

After establishing Descartes’ position, I raise the question, how did Descartes arrive at the idea that representation need not be by means of resemblance? I answer it by considering Descartes’ mathematical work. Descartes was the first to develop, independently and in parallel with Fermat, Analytic Geometry, in which algebraic entities (numbers and equations) represent and are represented by geometric ones (points, lines and other figures). For instance, the representation of equations by means of graphs enables one to solve the equations by making the corresponding drawings. This was a natural development in the mathematics of the age, for reasons I shall mention in my talk. The interest in developing a mathematical physics made Descartes first apply geometry as a tool to represent aspects of perception, and later – once he geometrised bodies under Galileo’s influence – to incorporate structural representation into his physiology and metaphysics of perception. In this way, transferring insights from one domain (mathematics) to another (perception), Descartes managed to revolutionise our understanding of perception.

What Happened to the Distinction Between Proper and Common Sensibles?

In Metaphysical Meditations, meditation one and two we can read the well-known passages where Descartes founds his epistemology and develops his doctrine of self-verifying premises as being the only true premises. At several points he analyses and refers to the senses, sense-experience and perception. For the reader familiar with Aristotle there is clear difference with the underlying consideration of the senses that we read in this foundational text by Descartes, namely that the distinction between common and proper sensibles is nowhere to be found. And yet this distinction has far reaching consequences for our understanding of the nature of knowledge. We will argue that the merging of this Aristotelian distinction is central to the starting points of Cartesian idealism.

In our paper we will first introduce this problem, secondly return to Aristotle’s De Anima to clarify what this distinction was, and then establish our claim that it is no longer present in Descartes by closely analysing the Cartesian texts. We will support our argument that the merging of proper and common sensibles is indeed an integral and continuous part of Descartes epistemology by including other texts by the philosopher where he considers the senses. Having established this we will briefly consider some possible historical influences which may lie behind this unexplained shift of perspective. This will include above all some consideration of Duns Scotus. We will then consider some consequences, and argue, as mentioned, that this Cartesian oublie is central to the better known Cartesian idealism. To our knowledge, literature on this precise topic is very scarce, if not non-existent. We will refer to the following authors: Aristotle, Descartes, Gilson, Ariew, Marion, and others.

Descartes on Responsibility and External Blame Attribution

This paper will explore the notion of responsibility in Descartes, in particular in his text The Passions of the Soul. In this text he says that we are responsible for our actions because these are preceded by a judgement in the Soul, regardless of whether these actions are responses to externally caused passions. These passions and subsequent judgements are experienced and judged by the individual, which suggests the individual is the only one privy to the internal machinations and the effort the soul has in managing them virtuously. The question then arises how eventual failures of the Soul can be determined externally – by the church, for example – if we can only gauge our responsibility for actions from our own perspectives and internal knowledge of good and evil.

I will argue that Descartes’ account of the Soul and its capabilities is insufficient in supporting the possibility of blaming others for their actions. It is unclear what the relation is between our inner sense of good and evil and external (religious) standards by which our conduct is evaluated. Ultimately I will show that what is missing in Descartes’ account is clarification on how our internal, subjective normative judgements can be related to external standards.

Early Modern Techniques for Managing Sense-Impressions: A ‘Sensitive’ or ‘Cognitive’ Cure?

Both theoretical and practical early modern discussions of the faculties and passions of the soul develop a set of strategies for achieving mental, bodily and moral well-being which focus on the activity of the external and internal senses alike and minimize the input of one’s rational faculties. Although the focus is on the faculty of imagination, these strategies, which have roots in both Stoic and medical sources, are comprised of variations on the techniques of redirecting one’s senses from disagreeable images towards agreeable ones, of refashioning one’s mental images in such a way so as to trigger favourable affective responses or of otherwise maintaining the powers of one’s sensitive soul in a heightened degree of activity. What is significant is that these techniques downplay the role of cognitive and discursive control and, instead, provide means of rectifying one’s judgements and passions through various exercises of perception alone. This feature is emphasized even further in eighteenth-century versions of such strategies which lay stress on the manner in which certain habits of perception are able to modify one’s affective response towards a particular external stimulus, without the need to alter the stimulus itself. Building on contributions signed by McMahon (1976), Jackson (1989, 1990), James (1998, 2006) and Lyons (2005), the aim of this paper is to examine this body of techniques across both seventeenth- (Wright 1601, 1604; Burton 1621; Reynolds 1640; Charleton 1674) and eighteenth-century (Dennis 1701, 1704; Addison 1712; Akenside 1744; Hume 1739-40; Hartley 1749) key discussions, in order to make out the role that each faculty plays when the mind resorts to such exercises and determine whether we are indeed dealing with a sense-oriented regimen or, rather, with a more nuanced collaboration amongst both sensitive and higher, intellectual powers of the soul.

Spinoza on Numbing, Dawning, and Vagueness

Spinoza famously holds that sensory perceptions, sadness, and other passions can be destroyed. Rendered impassive and desensitized, we make room in ourselves for ecstatic love. Bennett famously grumbles that this process requires that a passion can come to have begun differently than it began. I answer the complaint in the course of exploring two hitherto underattended parts of Spinoza’s philosophy of perception: aspect-dawning and perceptual vagueness.

What is an aspect? If you are teaching courses on “English as a second language” and “English as a political weapon” then these courses are about numerically distinct things. If you are writing an essay about “Janet Jackson as a gay icon” and another about “Janet Jackson as a humanitarian”, then these essays are about numerically distinct things. These curious things are aspects. Aspects are mind-independent, and irreducible to the properties of their bearers. A perception of an aspect is a perspective.

When we see something anew, we perceive a different aspect of it. Its apparent qualities change. We can describe this change as if it were a change in the thing itself. For example we may say, with a degree of propriety, that the Necker cube *flips*, that the word “pain” *loses its sting* when we read it in English and then in French, and that the chord B-D-F sounds fearful but *becomes sunnier* when a G is added.

To destroy a passion is to see it anew, under a new aspect. It is a change, not in the passion itself, but in what aspect of it we perceive. Or so I argue.

This interpretation acquits Spinoza’s theory of psychic liberation of Bennett’s charge of absurdity. It leads to another puzzle. According to Spinoza, a perfect mind represent things only under the aspect of eternity. It does not represent sensory perceptions and passions. It does not even represent them as not existing, nor as falsely appearing, to some, to exist! So if we could perfect our minds, we would become unable to represent the flaw we once had. Paradoxically, our *ability* to think about this cognitive flaw is a symptom of that very flaw.

I respond that, for Spinoza, passions and perceptions of passions are perceptually vague. (To do so, I defend George Eliot’s translation of “experientia vaga” at 2p40s2 as “vague experience”.) Spinoza thinks that the vagueness of our perceptions is a cognitive flaw in us. But all representations of vagueness are themselves vague. So he is correct to say that a mind that could not perceive anything vaguely would be unable to think anything at all about vague perception—even that others suffer from it, or that it is inadequate. We must blame the paradox not on him but on vagueness itself.

Shifts Towards Experimentation in Early Modern Natural Philosophy

I would like to present a chapter of my forthcoming book that investigates epistemic practices in the Life Sciences from a hands-on perspective. In Chapter Two I discuss shifts towards experimentation in seventeenth century natural philosophy, focusing on specialized contexts of experiences and the emergence of artificially designed scenes of knowledge in Western Europe (Schramm 2005). I argue that aesthetic issues are at the core of a rising experimental empiricism that lost its grounding in Aristotelian sense-based epistemology. With the rise of modern science as an experimental research practice, sensual perception became differentiated into ‘ordinary’ perception of everyday occurrences and an ‘aestheticised’ mode of perception that became invested with epistemological significance. For early modern experimenters, perception became intricately interwoven with processes of making and specialized contexts of experiences: what the ‘new scientists’ perceived, among which Marin Mersenne and René Descartes, was the outcome of a laborious process that involved the work of minds, hands, a skilled use of instruments and a deliberate training of the senses. This phase of transition away from an Aristotelian natural philosophy was marked by a “crisis of perception” and a call for new epistemologies that can account for knowledge making practices that rely on “strategies of aestheticisation” (Nelle 2005). I will present case studies of experimental work by Marin Mersenne (acoustics) and René Descartes (anatomical investigations) that make palpable how shifts towards experimentation and manipulation in seventeenth century natural philosophical inquiries brought about an epistemological dilemma.

I open this chapter with impressions of a practical introductory course into experimental life sciences at a Dutch University. Against the backdrop of participant observations from a contemporary life science training lab, I describe shifts towards experimentation in early modern natural philosophy. This multi-sited historico-ethnographical approach takes me from the bench in today’s instruction labs, in which students are trained to study life processes and phenomena on a molecular level, to the specialized contexts of experience where 17th century natural philosophers investigate phenomena that lie beyond the limits of human perception. Marin Mersenne (1588-1648) experimental inquiries into musical string vibrations and acoustic phenomena that manifest themselves outside the range of our ordinary are discussed as a case study to exemplify aesthetic issues which lay at the core of the “new scientist’s” epistemological dilemma. Drawing on the concepts of “aestheticisation” (Nelle 2005) and “engendering” (Lefèvre 2005), I describe how ‘scientific’ observation in early modern Europe became inherently dependent on hands-on practices of constructing particular spatial settings and experimental set-ups, skillful handling and making of instruments that either improve or alter our sensual apparatus, including strategies of staging and intervention (cf. Shapin and Schaffer 1985; Hacking 1983). This chapter thus provides a historical and epistemological grounding for a phenomenological analysis of instrument-body relations (e.g. pipetting), body techniques, and regimes of touch as well as “clean room aesthetics” in today’s life science laboratories that are discussed in the second part of my book.

Brain Research in the Seventeenth Century: Innovations and Superstitions

It was already known for centuries that the brain is important organ for our cognitive faculties, but much like contemporary scientists early modern philosophers struggled with understanding the relation between mind and matter. While the natural world and the human body were steadily being understood in mechanized terms, the human mind resisted reduction due to its complexity and perceived immaterialism. In the works of philosophers of that time where the brain is mentioned it usually plays an important cognitive role as the principle seat of reason or some other function. However, it remains vague how these philosophers thought the brain operated within the human body.

This paper tries to understand in what way Descartes, Hobbes and other philosophers in the 17th century held the brain responsible for the production of cognitive faculties. This research will start with an examination of Nicolas Steno, an anatomist and natural scientist who was responsible for important innovations in anatomical and neurological research during that time period. Studying Steno’s neurological research will be beneficial for us for two reasons. Firstly, we are able to understand the commonly held superstitions and established science of his time, knowing this we can extrapolate what other philosophers may have known. Secondly, Steno was on the forefront of anatomical innovations in his time and well acquainted with many other scientists, meaning that if we want to understand the propagation of newly developed anatomical theories in that time Steno is a good place to start. By establishing the neurological conceptions of the 17th century we can better understand the passages where philosophers mention the brain, fully appreciating their innovative thoughts regarding the workings of the mind and completing our interpretation of their works.

The Role of Perfection in Descartes’ Natural Philosophy

Descartes’ use of the notion of ‘perfection’ has received much attention in relation to his ontological argument for the existence of God. In contrast, relatively little has been written about the idea of perfection with regard to other facets of Descartes’ philosophy. In this paper, I critically examine the role of perfection in Descartes’ natural philosophy. I will argue that the concept of perfection, so important in Descartes’ theology and ontology, permeates his natural philosophy more deeply than hitherto admitted. I will focus on Descartes’ argument in Principles of Philosophy that the greater the objective perfection in our ideas, the greater its cause must be, and his discussion of the production of heat in objects in Meditations on First Philosophy. Through these examples, I will show that the link between perfection and cause for ideas finds a close parallel in the case of heat in objects. I then o er several further examples from Descartes’ writings pertaining to natural philosophy in order to demonstrate that a theory of perfection runs through this aspect of his thought, too.

The Birth and Development of Sir Isaac Newton’s Theory of Light and Colours

Sir Isaac Newton wrote a famous letter in 1672, meant for the Royal Society of London, in which he presented a new theory of light and colours, according to which colour is an original and connate property of light. Newton’s new theory was based on evidence he collected from experiments he had conducted between 1666 and the letter of 1672. This paper shows both the novelty and the evolution of Newton’s theory. It demonstrates the novelty by giving an overview of the precise nature of Newton’s disagreement with his, mainly Cartesian, predecessors regarding colours and light, and makes clear, based on the evidence we possess, including evidence from papers, notes and documents which were found after Newton’s death, how the theory evolved. The paper establishes that Newton’s suggestion in the letter of 1672 that he did not expect the views of his predecessors on light and colours to be wrong, but only encountered this, almost coincidentally, whilst doing experiments with his prism, is not in accordance with the available evidence. Newton did expect his predecessors to be wrong. Furthermore, the example of Newton’s theory of light and colours is used in the last part of the paper to argue for placing Newton among the most important philosophers of the Early Modern Period. Newton need, it is stated and defended, not solely be considered a scientist, in the modern sense, but deserves, based for example on his theory of light and colours, which has a philosophical component, to be given a prominent place within the history of philosophy.

Anticipation by Simulation: Adam Smith’s Theory of Perception

I argue that Adam Smith’s essay, “On the External Senses” (ES) accounts for an aspect of sensory perception often overlooked, our ability to anticipate tactile experiences associated with objects seen, heard and smelled at a distance, when those tactile experiences require contact with our bodies. On Smith’s account, when we perceive objects by senses other than touch, we simulate these objects as being the proper objects of touch and evaluate their significance to our body’s health or harm. When we see an the tip of a sharpened spear, we simulate its painful e ects on our body—we imaginatively place ourselves in proximity to the object and feel some measure of the pain we naturally associate or have learned to associate with its presence (ES, 54; see also ES, 55, 58). When we smell good food, our mouths water with the pleasure we anticipate will result from eating it. (ES, 80) When we hear a loud sound, we automatically shrink with fright in anticipation of the pain we imagine would be caused by such an object. (ES, 87) As Adam Smith writes, the senses “instinctively suggest to us some conception of the solid and resisting substances which excite their respective sensations.” (ES, 75)

Language and Perception as the Foundation of Knowledge by Early Modern Philosophers

In current writings on the philosophy of perception, reference is often made to the notions of how, Western, early modern philosophers perceived the world. However, focussing solely on perception gives an incomplete picture of the philosophical debates, from Descartes to Condillac, and their epistemological notions. This article argues that perception is frequently seen as the cornerstone of knowledge, in which language had a vital role to fulfil: the translation of perceptions into public knowledge. In doing so, this article analyses three problematic points in the translation process of perception into language: first, the limitations of perception; second, to which extent does perception provide knowledge; third, the restrictions of (natural) language. Early modern philosophers tried to solve these problems which resulted in the development of artificial languages in the seventeenth-century by John Wilkins and George Dalgarno, and the much-debated topic by philosophers: the origin of language, in the eighteenth-century. In reconstructing philosophical debates about perception, by using publications and private letters of early modern philosophers, we can conclude that perception was only part of a much broader discussion in the philosophical landscape of the early modern period, which is a di cult topic to study in isolation.

The Tension Between Reason and Experience in Early Modern Aesthetics

Aesthetics as a scientific discipline gained profound prominence in the middle of the 18th century with the publication of Baumgarten’s Aesthetica. However, it is mistaken to believe that the subject was regarded as incompatible with scientific methods by his predecessors in the previous century. In this paper it will be argued that the period formed an indispensable foundation for the developments in this field. Accordingly, we should not consider Baumgarten’s theory as a fundamental break with rationalist inspired aesthetics, but a process that followed from Cartesian principles and methodology. In the 17th century, the effects of aesthetic experience needed explanation in the form of general principles in order to be free of the charge of chance. In his Essay on Criticism (1711) Alexander Pope ascribes to art the function of imitating nature, as a representation of the universal in the particular through the means of reason. Individual, empirical experience obscures the clarity good art should portray. Yet any aesthetic argument must always include empirical premises. How can aesthetics then be founded on Reason? How was the tension between Reason and experience resolved? This conflict resulted in skepticism about the belief that all art should answer to one general principle derived from nature. It will be concluded that 17th century aesthetics did allow for individual experience to compete with the principle(s) of art, as explicated by Dryden and Reynolds, amongst others, and that aesthetics is not a unique invention of the mid-18th century.

Perceiving Depth and Distance in Vision: Descartes’ Reversal of Kepler’s Optics

How do we perceive things with the dimension of depth? Before this question was dealt with by psychology, it was at the core of the science of optics. In this talk, I would like to show how Descartes took up from Kepler’s Ad Vitellionem Paralipomena a psychological procedure involved in vision and consisting in a trigonometric operation to account for the

location and distance of objects in three-dimensional space. But, whereas Kepler had resorted to this procedure to account for the illusory, imaginary location of objects seen through reflection or refraction, Descartes applied it to the perception of distance in non-deceptive direct vision. I will show that this brings about a complete shift regarding the epistemological value of the psychological operations involved in vision.