George Berkeley 16851753

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George Berkeley (1685-1753)

• British empiricist
• Held that the only objects of human knowledge are
  ideas and the minds that have the ideas
• Hence, Berkeley is an Idealist (as opposed to a
  Materialist)

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Modern theory of Ideas

• ideas are formed in three ways
• directly imprinted on the senses
• introspected in the mind (passions, emotions)
• formed by memory and imagination

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Esse is percipi

• Berkeley holds that since we can only have
  knowledge of ideas and our minds, those are the
  only things we have reason to posit as existing.
• Hence, to be is to be perceived (esse is percipi)

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Bs argument against positing material substance

• P1. Only our sense perceptions give us reasons to
  posit existence, and the only things that appear
  to our senses are ideas.
• P2. Ideas are not material substances.
• C. Hence, we have no reason to posit the
  existence of material substance.

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Bs refutation of primary/ secondary quality
distinction

• P1. Secondary qualities exist only in the mind.
• P2. If primary qualities are inseparably united
  with secondary qualities, then they exist only
  in the mind.

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• P3. It is impossible to separate our ideas of
  primary qualities from ideas of secondary
  qualities.
• C1. Therefore primary qualities are inseparably
  united with secondary qualities.
• C. Therefore, primary qualities must exist only
  in the mind.

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Bs argument against material substance

• P1. If we can know that there is material
  substance existing apart from the perceiver, then
  either we know it by sense or reason.
• P2. We cannot know of something that exists
  unperceived by our perceptions. Hence, if we
  know that material substance exists apart from
  perceivers, it must be by reason.

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• P3. The only things we can know by reason are
  things that can be inferred from our sense
  perceptions (empiricist premise).
• P4. There is no necessary connection between
  material substance and perceptions, so we cannot
  infer material substance from our perceptions.
• C. Therefore we cannot know that material
  substance exists.