Reason as a Source of Knowledge

• Proof of the External World


  Descartes' argument that his sensations of objects cannot come from inside him and must be caused by the external world.
• Ontological Argument


  Descartes' argument that the idea of a supremely perfect being (God) includes the property of existence, therefore God must exist.
• Contingency Argument


  Descartes' argument that his own existence proves the existence of God, as the cause of his existence must be either himself, his parents, or God.
• Trademark Argument


  Descartes' argument that the cause of his idea of God must be God Himself, as a perfect being can only cause the idea of a perfect being.
• Cogito

  Descartes' statement 'I think, therefore I am,' which is a self-evident truth that proves one's existence.
• Hume's Fork


  Hume's division of human understanding into relations of ideas (revealed by reason) and matters of fact (derived from experience).
• Tabula Rasa


  Locke's theory that the mind is born as a blank slate and all ideas and concepts are derived from experience.
• Argument from the Necessity of Truth


  Leibniz's argument that certain truths, such as mathematical truths, are necessary and can only be known through reason, which is based on innate principles.
• Leibniz's Innate Ideas


  Leibniz's belief that the human mind can gain knowledge through reason, prompted by the senses, and that we have innate ideas or principles revealed by reason.
• Plato's Innatism


  Plato's belief that we have forgotten innate ideas, but through reasoning, we can regain a perfect understanding.
• Innatism


  The philosophical claim that we are born with certain knowledge, which can be revealed through reason.
• A priori knowledge


  Knowledge that is justified independently of experience and can be known with certainty before experiencing it.
• A posteriori knowledge


  Knowledge that is justified based on experience and cannot be known with certainty before experiencing it.
• Rationalism


  The philosophical claim that reason, by itself, can be a source of knowledge.
• Empiricism


  The philosophical claim that our knowledge is primarily derived from experience and evidence obtained through our senses.
• Method of doubt

  • Descartes thought to subject all knowledge to extreme scrutiny - if it can be doubted, then it is not secure
  • Clear and distinct ideas: ideas that are irrefutably true and stand up well to doubt
• Issue w/ clear and distinct ideas

  • few examples from descartes of clear/distinct ideas -> 'i am thinking' and '2+3+5'
• Cartesian intuition and deduction - 2 operations of the mind

  • c/d ideas - undoubtable
  • descartes argues that humans are open to intuition and from that intuition they can deduce certain things about the world
  • intuition -> inwardly 'looking upon' a concept and seeing its true features
  • ie doing a simple sum, descartes thinks this can be extended to other knowledge
• Cartesian deduction

  • deduction is the ability to take those ideas and form logical conclusions from them
  • reasoning from self-evident truths (intuition) to more complex conclusions
  • ie 1. a=b
  • 2. b=c
  • 3. therefore a=c
• Descartes Foundationalism

  foundationalist approach -> create a system of knowledge from its foundations

  intuition/deduction -> applied to the world would mean more secure basis of what is considered knowledge

  all knowledge can be deduced from clear and distinct ideas which are a priori
• Empiricist responses to intuition and deduction thesis

  Hume:

  • argued that deductive arguments give you the truth but no new information about the world
  • only inductive arguments based on actual experience of the world give new info