Scientific Realism: Appearance and Reality Reality what a concept Ian Hacking

2 Scientific realism  Metaphysical questions: Appearance and reality  Key terms: 1) Metaphysical realism 2) Direct realism 3) Ideaism 4) Causal realism

3 Why metaphysical questions?  Science appears to tell us the fundamental structures of the world in which we live: the composition of matter and the physical laws which they obey  Regardless of the nature of scientific method and how we justify knowledge claims in science, there are questions about whether we ought to believe what scientific theories tell us about reality beyond the appearance of things.

4 Appearance and reality: The two tables  The ‘ordinary’ table: “[It] has been familiar to me from earliest years. It is a commonplace object of that environment which I call the world. How shall I describe it? It has extension, it is comparatively permanent; it has colour; above all it is substantial. … It is a thing” Arthur Eddington, The Nature of the Physical World, cited on p. 131

5 Appearance and Reality  Contrast the ‘scientific’ table: “It does not belong to the world previously mentioned—that world which spontaneously appears around me when I open my eyes. It is part of a world which in more devious ways has forced itself on my attention. My scientific table is mostly emptiness. Sparsely scattered in that emptiness are numerous electric charges rushing about with great speed; but their combined bulk amounts to less than a billionth of the bulk of the table itself” Eddington, p. 131

6 Common sense vs. scientific world  Do both—the commonsense (appearance) & scientific (reality)—tables exist? What is the relation between the two ‘worlds’?  This question of ‘appearance’ and ‘reality’ gained prominence during the scientific revolution in the 17 th Century. However, the question of ‘appearance’ and ‘reality’ dates back to the beginning of Western philosophy  E.g. the early Atomists’ solution

7 Historical roots: scientific revolution  The key analogy used in the scientific revolution the is to compare Nature to a giant clockwork mechanism: Inner mechanisms produce outward appearance  Science aims at understanding the inner mechanisms responsible for our observations  So we perceive with our senses may not be properties that things have in reality

8 Scientific revolution  Philosophers who supported the scientific revolution held that objects were made up of corpuscles (recall the atomists’ solution).  Locke’s example: gold  How does gold appear to us? How do we know that those features that appear to us are gold’s essential properties?

9 Primary vs. Secondary properties  What is responsible for gold’s appearance?  Locke used the terms ‘real essences’ for primary properties, and ‘nominal essences’ for secondary properties.

10 Primary vs. Secondary properties  Descartes’ wax example: “It has been quite freshly from the hive, and it has not yet lost the sweetness of the honey which it contains … its colour, its figure, its size are apparent; it is hard, cold, easily handled …But notice while I speak and approach the fire what remained of the taste is exhaled, the smell evaporates, the color alters, the figure is destroyed, the size increases, it becomes liquid” Descartes, Meditations of First Philosophy

11 Primary vs. Secondary properties  Primary properties: “those properties that things not only appear to have, but which they also have in reality” (Ladyman 134)  Secondary properties: “those [properties] which things appear to have but which they don’t possess in themselves, only in the mind of the observer” (ibid.)  Here think about color, odor. Are they properties that an object have in reality, i.e. independent of us, or do they depend on the observer?

12 Primary vs. Secondary properties  Primary properties are those that exist in an object whether we perceive them or not; Secondary properties do no exist unperceived  Primary properties have the disposition, or power, to produce a particular kind of sensation (say the color yellow) in us, but there is nothing resembling our experience of color in the primary properties themselves

13 Primary vs. Secondary Properties  What are examples of primary properties?  Extension—properties that are quantifiable (137)  Eddington’s scientific table is made up of primary properties described by today’s science; his everyday table bears the secondary properties of everyday experience  What is the relation between our experience of things and their primary properties? How can know about the primary properties of things since they are not observable (inner mechanism)?

14 Metaphysical issues: variety of realisms  Metaphysical Realism: “our ordinary language refers to, and sometimes say true things about, a mind independent world” (138).  What does mind-independence mean?  The issue for philosophy of science is not whether the objects described by science exist but how we can know that they exist and what their natures are (ibid)

15 Direct Realism  One solution to the question of how we can know that they exist and what their natures are is ‘direct realism’  Direct realism: “there are external objects that exist independently of our minds and which we directly perceive with our senses” (139).

16 Direct realism  Arguments against direct realism: 1) Illusions 2) How sense perception really works— contribution by our brains

17 Ideaism  Perhaps what we perceive in our minds are ‘ideas’, or ‘representations’  The view that “the immediate objects of perception is ideas in the mind, rather than objects in the external world” is call Ideaism (140)  First distinguish between ‘ideas’ and ‘impressions’  ‘Impression’ is what is forced on the mind by the senses; ‘Idea’ is the image of that impression that one can bring before our mind at will (141)

18 Ideaism  Ideaism is a theory about perception  Ideaism contradicts direct realism; it does not, however, say that there are no external objects  Objects in the world cause the impressions we have of them  Causal realism: “there are external objects that exist independently of our minds and which cause our indirect perception of them via the senses” (141).

19 Consequences of causal realism  Once we adopt causal (representative, or indirect) realism, we have a gap between the world as we perceive it and the world as it is.  The gap gives rise to skepticism, that we may be massively mistaken about the external world  Next time, we’ll discuss solutions to the epistemic gap introduced by representative realism