The Science of Human Nature

1. The Science of Human Nature • Molyneux’s Question • Suppose a Man born blind and now adult and taught by his touch to distinguish between a Cube and a Sphere of the same bigness, so as to tell, when he felt one and t’other, which is the Cube, which is the Sphere. Suppose then the Cube and Sphere placed on a Table, and the Blind Man to be made to see. Quaere, whether by his sight, before he touch’d them, he could now distinguish, and tell, which the Globe and which the Cube. • What is the nature of human knowledge? • Berkeley & Hume – Idealist & Skeptic (but both empiricists) • Kant – A return to Metaphysics.

2. George Berkeley (1685-1753) • esse is percipi, - to be is to be perceived • He was an idealist - everything that exists is either a mind or depends for its existence upon a mind • He was an immaterialist – matter did not exist except in the mind. • Best known for two books • An Essay towards a New Theory of Vision (1709). • A Treatise concerning the Principles of Human Knowledge (1710)

3. A New Theory of Vision • The aim of the New Theory of Vision was • "to shew the manner wherein we perceive by sight the distance, magnitude, and situation of objects. Also to consider the difference there is betwixt the ideas of sight and touch, and whether there be any idea common to both senses" (NTV §1) • He distinguishes between two kinds of perception • Mediate – indirect • E.g. we perceive pleasure by perceiving a smile on someone’s face. • Immediate – direct • E.g. we perceive sensory information directly. • There is no way to demonstrate the extension of things in the world except through ideas (percepts).

4. The Perception of Distance • So, what are the immediate ideas that mediate the perception of distance? • Kinesthetic sensations are associated with focusing the eyes when perceiving objects at various distances • As objects are brought closer to the eye, their appearance becomes more confused • Third, as an object approaches the eyes, the degree of confusion can be mitigated by straining the eyes, which is recognized by kinesthetic sensations • Thus there is no necessary connection between the ideas and distance, merely a customary connection between two types of ideas

5. Touch & Vision • Like most enlightenment philosophers Berkeley assumed that touch provides immediate access to the world. • Berkeley claims that visual ideas are merely signs of tactile ideas. • There is no resemblance between visual and tactile ideas. • Their relationship is like that between words and their meanings. • If one hears a noun, one thinks of an object it denotes. • If one sees an object, one thinks of a corresponding idea of touch • In general Berkeley follows the heterogeneity thesis • The objects of sight and touch and each of the other senses are distinct and incommensurable. • So, one complex tactual object corresponds to the indefinitely large number of visual objects. • Since there are no necessary connections between the objects of sight and touch, the objects must be distinct.

6. Against Abstraction • Berkeley had a distinct dislike of uncertainty with respect to human knowledge • He blamed philosophical skepticism on both abstraction and materialism. • Locke’s theory of abstraction • Abstraction explains how general terms obtain meaning • E.g. A general term, such as ‘mouse' refers to an abstract general idea, which contains all and only those properties that one deems common to all mice, or, more properly, the ways in which all cats resemble each other. • Berkeley’s response • (1) "I can’t do it" • (2) "We don't need it" • (3) “The theory leads to inconsistencies"

7. Against Materialism • Berkeley’s attack on materialism is an attack on how material objects come to be represented. • The argument is essentially • We perceived ordinary objects (chairs, cars, houses, etc) • We perceive only ideas • Therefore ordinary objects are only ideas • However, the representational materialist can use the distinction between mediated and immediate perception to reply • Ordinary objects of mediately perceived • Ideas are immediately perceived • Berkeley replies that essentially this is nonsense • The representations of the represented objects are ideas and not the objects themselves • This antimaterialist stance is essentially dualist – how can material objects cause mental ideas?

8. David Hume (1711-1766) • He is perhaps the most important of the British empiricist philosophers (he was Scottish, born in Edinburgh) • His best known work is the Treatise of Human Nature (1739/40). It was not well received but was adapted and later published as • Enquiry Concerning Human Understanding • Enquiry concerning the Principles of Morals • He was remarkably unpopular among the religious hierarchy • He argued against miracles, against life after death and in favour of a person’s right to commit suicide.

9. Empiricism writ large… • In Enquiry concerning the Principles of Morals he wrote that we should • "reject every system...however subtle or ingenious, which is not founded on fact and observation," and "hearken to no arguments but those which are derived from experience“ • All our thought is derived either from sensation ("outward sentiment") or from reflection ("inward sentiment") • Hume stated that • Complex ideas are composed of simple ideas and thereby limited by our simple ideas which are copies of our sensory impressions • But he claimed that this is an empirical not a metaphysical statement.

10. The Empirical Method • Hume’s philosophical skepticism led him to conclude that when a • "philosophical term is employed without any meaning or idea (as is too frequent), we need but enquire, from what impression is that supposed idea derived? • His method is both simple and devastating • Find the idea to which a term is annexed. If none can be found, then the term has no content, however prominently it may figure in philosophy or theology. • Then, if the idea is complex, break it up into the simple ideas of which it is composed. Then trace the simple ideas back to their original impressions • “By bringing ideas into so clear a light we may reasonably hope to remove all dispute, which may arise, concerning their nature and reality” (Essay on Human Understanding)

11. Associationism • The means by which ideas connect to become more complex are not simply rational, rather they reflect the ‘natural’ activity of the mind. • Principles of connexion • Resemblance • Contiguity • Cause and Effect • The relationship between cause and effect is difficult, • Causes and effects are distinct events: we can imagine the causal event occurring without the effect (e.g. sex and pregnancy) • The external reality • "an object, followed by another, and where all objects similar to the first are followed by objects similar to the second“ • Internal experience • "an object followed by another, and whose appearance always conveys the thought to that other"

12. Immanuel Kant (1724-1804) • Born to a wealthy Lutheran couple in Konisberg, East Prussia. • He is perhaps best know for his book A Critique of Pure Reason (1781/7) • He is often considered one of the most important philosophers of all time and he addressed a fundamental question • "What can we know?" • His answer • Our knowledge is limited to mathematics and the empirical, natural sciences. • Knowledge cannot extend to metaphysics (e.g. God) • The mind is active in constructing the features of experience and the mind activity is limited to the empirical reality of space and time.

13. Rationalism vs Empiricism • Rationalism vs Empiricism • The empiricists argue that all human knowledge is known a posteriori • The rationalists argue that at least some human knowledge is known a priori • Kant argued that any theory of knowledge that relies on the distinction between a priori and a posteriori is destined to fail • A further distinction between synthetic and analytic knowledge is needed • Analytic - the predicate is contained within the subject. • "Every body occupies space" - to occupy space requires you to have a body • Synthetic – the predicate is not contained with the subject • “It’s cold and sunny today” – there’s nothing about “today” that necessitates “cold and sunny”

14. Synthetic A Priori Knowledge? • The problem for the empiricists is that some of the foundations of their theories cannot be known a posteriori. • “Every event must have a cause” or “Moving objects are moved by a mover” • According to Kant these kinds of statements are both synthetic and a priori and empiricism fails as a theory of what can be known because of this • Kant’s solution to this problem is to argue that there are some things that the minds knows that shape our understanding of our sensory experiences. • His argument is that the nature of our experience of the external world must be as much about the features and activity of the mind that knows it as the external world itself. • Essentially, Kant is introducing a transcendental mode of argument. • "I call all knowledge transcendental if it is occupied, not with objects, but with the way that we can possibly know objects even before we experience them."

15. The Kantian Mind • Kants view of the Mind is relatively complex but it serves as the foundation for modern theories of cognition (especially with cognitive science) • The mind is constituted by a set of complex abilities (functions) • Thinking requires both percepts (on the basis of our sensory experiences) and concepts (cognitive functions that shape our perception) • These functions operate a synthesis within the mind • To understand the mind is to understand those hidden, unobservable mental functions. • Synthesis • “By synthesis, in its most general sense, I understand the act of putting different representations together and of grasping what is manifold in them in one knowledge”