St Thomas Aquinas

God's Existence

  • Argued for God's existence with a cosmological argument
  • Definitions
    • Effect --> something that has come to exist
    • Efficient cause --> something that brings an effect about (causes it to exist)
    • God --> first, uncaused efficient cause
      • If God is uncaused (not an effect), God must be something that did not begin to exist
      • God has always existed
  • Used process of elimination for existence of a first cause
    • Four possibilities
      • Regress has no end, it's infinite
      • Regress has no end, it's circular
      • Regress does have an end, something causes itself
      • Regress does have an end, there's a first cause (that is uncaused)
    • St Thomas Aquinas argues the first three possibilities are not possible therefore, God is the first cause


  • Deductive argument
  • Phase 1
    • There are causes and effects in the world
      • Not everything has a cause but every effect has a cause
    • In finite time, it's impossible to get through an infinite number of causes
      • No effect would ever be reached
      • There cannot be infinite causal regresses
  • Phase 2
    • Causes must precede its effect
      • There cannot be circular
      • There cannot be self-caused
  • Phase 3
    • We cannot have infinite, circular, or self-causation
    • The must be a first uncaused cause
  • Phase 4
    • Definition of God --> first, uncaused cause
    • God exists

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