• Central Role of Arguments
  • Philosophy is the investigation by rational argument of fundamental issues.
  • Philosophers investigate the issues by framing hypotheses and developing and evaluating arguments.
  • An argument is a piece of reasoning, from premises to a conclusion.
• Arguments improve over the centuries
  • Descartes vs Hume, for example
• Rationalism vs Empiricism
  • Rationalism is the view that
    • Important truths about the world can be established by a priori reasoning, i.e. by logical deduction from self-evident truths.
      • A priori means independent of experience.
  • Empiricism is the view that
    • Important truths about the world can only be established by a posteriori reasoning.
      • A posteriori means based on experience.
• Approach to Philosophizing (Doing Philosophy)
  • Some philosophers put forth fundamental theories of everything.
    • Descartes, Spinoza, Kant
  • Others address philosophic issues one at a time.
    • G.E. Moore
• Ontology
  • The ontology (or ontological commitment) of a theory consists of the kinds of entities it postulates.  For example,
    • Idealism: only minds and mental phenomena
      • Berkeley, Bradley
    • Materialism: only physical objects and processes
      • Thomas Hobbes
    • Monism: only one kind of substance
      • Spinoza
    • Dualism: two kinds of substance, mental and physical.
      • Descartes
• Extreme Metaphysics vs Common Sense
  • Extreme Metaphysics
    • Some philosophers have argued there are no physical objects, time is unreal, and tomatoes aren’t red or any other color.
  • Common Sense Worldview
    • The worldview of common sense and science.
      • The universe consists of physical objects, atoms, subatomic particles, radiation, energy, space, and time.
      • Perception and memory are for the most part reliable.
      • Events are generally caused.
      • The universe runs according to laws of nature.
      • Human beings and some animal species are conscious.
• Skepticism vs Common Sense
  • Skepticism
    • There’s no rational basis for believing, for example, that there are physical objects, other human beings are conscious, and there will be a sunrise tomorrow. No one knows whether these things are true.
  • Common Sense Worldview
    • It’s rational to believe the worldview of common sense and science. Everyone knows there are physical objects, other human beings are conscious, and there will be a sunrise tomorrow.
• Role of Math and Science
  • Developments in math and science have affected philosophy significantly
    • Mathematical Proof
      • Proof in Euclid’s Elements that √2 is irrational
    • Axiom Systems
      • Euclid’s axiomatic development of plane geometry
    • Scientific Theories
      • Newton’s laws of motion and his theory of gravitation