Thomas Aquinas: Arguments for God

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Thomas Aquinas Arguments for Gods Existence

• Kinds of Arguments and the Argument from Motion
• January 14, 2004

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Overview

• A priori and a posteriori arguments.
• Why Prove Gods Existence?
• The Arguments
• Argument from Change
• Argument from Causation
• Argument from Contingency
• Argument from Degrees of Excellence
• Argument from Harmony

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Next Time

• Just as it says on the syllabus
• Do SQ 4, p. 49
• Do FFR 3, p. 51

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A Priori and A Posteriori Arguments

• A Priori Arguments
• Premises dont require any empirical
  information.
• Instead, the argument proceeds purely
  conceptually.
• Ex All bachelors are unmarried men, and no
  unmarried men have wives. Therefore, no bachelors
  have wives.
• A Posteriori Arguments
• Premises do require empirical information.
• They require particular, contingent information
  about how the world is, beyond just conceptual
  information.
• Ex If the streets are wet, then my basement is
  flooded. But my basement is not flooded, so the
  streets are not wet.

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Why Prove Gods Existence?

• There are some reasons for doubting Gods
  existence.
• The Problem of Evil
• Occams Razor

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The Argument from Change

• Motion is used in its general sense, to mean
  change.
• What is the basic idea of this argument?

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The First Way Simplified

1. Things move and change.
2. Whenever something moves or changes, its motion
   or change must be caused by some other thing, not
   by itself or by nothing.
3. If that other thing is also moving or changing,
   then its motion or change must be caused by some
   further thing still.
4. If the chain of causes of changes stretched back
   infinitely, it would have no first link to get it
   started.
5. So, the chain of causes of changes does not
   stretch back infinitely.
6. So, there must be some First, Unmoved Mover,
   namely God.

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Whats All This Potentiality Stuff?

• It all depends on a lot of medieval philosophy
  you dont know.
• But, we can fix that a little bit
• A property is a feature of something redness,
  hotness, blandness, perfection, etc.
• To change is to gain a property or to move to a
  different place on some scale.
• Think of properties as contagious I cant gain a
  property without the intervention of something
  that already has at least as much of it as I wind
  up with.
• This means nothing can cause changes in itself
  changes have to come from the outside.