Rationalism: Knowledge Is Acquired through Reason, not the Senses

1
Rationalism Knowledge Is Acquired through
Reason, not the Senses

• We know only that of which we are certain. Sense
  experience cannot guarantee certainty, so all
  that we know comes from reason alone and is a
  priori (i.e., prior to experience)
• Our (innate) knowledge of certain propositions
  is based on remembering truths acquired
  before birth

Plato (427-347 BCE)
2
Empiricism Knowledge about the World Is A
Posteriori (Based on Experience Alone)

• At birth the mind is a blank slate (tabula
  rasa), containing no innate ideas. Even
  if some ideas were known universally, that
  does not prove they are innate
• Knowledge comes from sensation or reflection
• Ideas of primary qualities (e.g., solidity,
  shape) represent things as they really are ideas
  of secondary qualities (e.g., colors) represent
  things only as they appear to us

John Locke (1632-1704)
3
Naïve Realism We Do Not Perceive Ideas We
Perceive Their Objects
John Searle

• Perceptions are always intentional, that is,
  about something and when our perceptions are
  caused by the things they are about, we can be
  said to know those things
• Perceptions are not purely passive they are
  affected by ones background knowledge and beliefs

4
Analytic and Synthetic Judgments
Immanuel Kant (1724-1804)
David Hume

• Hume propositions are either relations of ideas
  (analytic, a priori) or matters of fact
  (synthetic, a posteriori)
• Kant propositions in mathematics (7512) and
  metaphysics (all events have causes) are
  synthetic a priori judgments
• Quine meanings of terms in even a priori
  analytic propositions depend on experience