4: Doubt and Knowledge



Key Terms

Cogito Ergo Sum
Wax Argument
Innate Ideas
Tabula Rasa
Subjective Idealism

  • Read and analyze a description of philosophical thought
  • Articulate key conceptual distinctions between modern views of reality
  • Articulate key conceptual distinctions between rationalism and empiricism
  • Demonstrate knowledge of Cartesian Doubt, the Wax Argument for Rationalism, Innate Ideas, Locke’s Tabula Rasa, and Subjective Idealism.

I. Descartes, Locke & Berkeley in Brief

  • Descartes
    • First modern philosopher
    • Cogito Ergo Sum
    • Application of doubt
    • Self-Evident truths
  • Locke
    • Reasonableness of doubt
    • Common sense
    • Opposed to the Theory of Innate Ideas
  • Berkeley
    • To be is to be perceived
    • Strong Empiricist leanings

II. Descartes (French Catholic)

  • A. Leaving the Dark Ages
    • Authority in the Medieval World: Church
    • Change initiated by Protestant Reformation, Scientific Revolution, Rise of Universities, Printing Press
    • Rediscovery of Classical Philosophy
  • B. Methodological Skepticism
    • What does it mean to be certain?
    • Certainty means inability to doubt
    • So subject all beliefs to doubt to find the foundation that is undoubtable
  • C. Method of Doubt
    • Step 1 Doubt the Senses (Optical Illusions)
    • Step 2 Doubt the Physical World
    • Step 3 Doubt Mathematics
  • D. The Undoubtable Foundation
    • Cogito Ergo Sum = I think, therefore I am
    • This is clear and distinct, or undoubtable
  • E. Wax Argument for Rationalism
    • Observing the difference between wax at room temperature and heated wax
    • Reason tells us that room temperature and heated wax are the same though physical properties are different

III. Locke (British)

What is Subjective Idealism?

Matrix Clip Link

  • A. Empiricism
    • Rationalism opens the door to speculations that are unsupportable and impossible to prove
    • Common sense dictates we follow the direct data of experience
  • B. Tabula Rasa and the Theory of Innate Ideas
    • Locke is opposed to the Theory of Innate Ideas
    • Argues against Universalism
    • We are born a tabula rasa (blank slate)
    • Liebniz disagrees, saying the human mind is born with innate inclinations and tendencies
    • Contemporary research supports Liebniz, not Locke

IV. Berkeley (Irish–British) 

  • Subjective Idealism
    • Takes empiricism to the next level
    • Objects do not exist independently of consciousness
    • The only things that exist are conscious minds and the ideas subjectively present to the conscious mind
    • Physical objects are groups of sense experiences
    • To be is to be perceived

Logic Week 4: Dysjunctive Syllogism