Scientific Realism: Appearance and Reality

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Scientific RealismAppearance and Reality

• Reality what a concept
• Ian Hacking

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Metaphysical issues

• Key terms
• Primary (Reality) vs. Secondary (Appearance)
  properties
• Metaphysical realism
• Direct realism
• Idea-ism
• Causal realism

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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 dont
  possess in themselves, only in the mind of the
  observer (ibid.)
• Primary properties possess the disposition to
  produce a certain type of sensation in us, but
  there is nothing resembling in our
  experience-secondary properties-in the entity
  itself.

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Metaphysical issues variety of realisms

• Metaphysical Realism our ordinary language
  refers to, and sometimes say true things about, a
  mind independent world (138).
• Mind independent means that those entities that
  exist would continue to do so even if no human
  beings are around

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Direct Realism

• How we can know that entities exist and what
  their natures are?
• Direct realism there are external objects that
  exist independently of our minds and which we
  directly perceive with our senses (139).
• Direct realism is problematicthe science of
  perception tells us that the brain plays a
  significant role in perception

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Idea-ism

• What we perceive in our minds are ideas, or
  representations
• Idea-ism the immediate objects of perception is
  ideas in the mind, rather than objects in the
  external world (140)
• Ideaism is a theory about perception
• Ideaism contradicts direct realism it does not,
  however, say that there are no external objects

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Idea-ism

• The companion realist position holds that 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).

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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 scepticism, that we may be
  massively mistaken about the external world

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Idealism alternative to causal realism

• George Berkeley (1685-1783) who argued for a
  position called immaterialism
• We experience only impressions and ideas but
  not matter (Idea-ism)
• All our ideas come from experience (Empiricism)
• The word matter cannot stand for any ideas and
  are therefore meaningless (Immaterialism)

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Immaterialism

• Berkeleys point is that since we do not
  experience matter directly.
• We experience ideas and impressions
• As an empiricist, he holds that all our ideas
  are derived from experience
• So we do not have an idea of the abstract notion
  of matter which is beyond experience

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Berkeley on primary vs. secondary properties

• Furthermore, Berkeley denies the primary and
  secondary property distinction. Here are two
  arguments.
• Recall the argument against matter. Try to
  imagine a material body without any colour at
  all.
• Berkeley argues that we cannot. The result is
  that we cannot separate secondary (colour) from
  primary (extension) properties.

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Berkeley on primary vs. secondary properties

• Another argument Secondary properties are
  supposed to be relative primary properties are
  stable
• What is cold to my touch, may not be to you. But
  not so with extension.
• However, Galileos tower example shows that
  motion itself is relative to a frame of
  reference. So even primary properties are relative

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From Idea-ism to Idealism

• For Berkeley, all properties are secondary that
  is there are no mind-independent ( primary)
  properties
• Furthermore, Berkeley holds that entities exist,
  but they do not exist independent of being
  perceived, i.e. independent of the mind.

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Idealism

• We perceive such things as trees and stones
• We perceive only ideas and their aggregates
  (Ideaism)
• Ideas and their aggregates cannot exist
  unperceived
• Therefore, trees and stones are ideas and their
  aggregates, and cannot exist unperceived
  (Idealism).

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Idealism

• Idealism metaphysical thesis that all that
  exist is mental in nature, hence it is
  incompatible with any form of metaphysical
  realism (144).
• Berkeleys point is that if you accept Idea-ism
  (and by implication, causal realism), the end
  result is scepticism
• He believes that his idealism is more faithful to
  our experience

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Idealism

• Possible objection against Berkeley what keeps
  the world as perceived going?
• God

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The aftermath of Berkeleys Idealism

• Kant agrees that there is a mind-independent
  world, except we cannot know it
• Kant distinguishes the world in itself (noumenal)
  and the world we experience (phenomenal)
• The phenomenal world (the world of experience) is
  Euclidean and Newtonian.
• We can have knowledge of such conditions for the
  possibility of experience a priori.