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C H A P T E R  11

 St. Thomas Aquinas

 St. Thomas Aquinas



  Saint Thomas Aquinas (1225-1274) 49 years

Dominican Order





1.  He was an Italian Dominican priest.

     His family locked him in a tower because

     The Dominicans are unconcerned with wealth and power.

2.  He is considered the Catholic Church's greatest theologian.
3.  He interpreted Church doctrine through Aristotle - not Plato.

     Problems - Aristotle believed that:

     a.  Life requires a soul, so man is mortal.

     b.  The universe is eternal - with no beginning.

     c.  God creates unknowingly.

4.  He wrote 25 volumes. His most influential works are:

     Summa Theologica and Summa Contra Gentiles.





1.   Faith in reason and an intelligible Universe are necessary for philosophy.

2.   Knowledge of revelation is known by faith.

3.   Knowledge of nature is known by reason and experience.

4.   Prior to experience the mind is a blank slate. (Aristotle)

      There is no innate knowledge.

      Our idea of God is also not innate. (Descartes)

5.   The senses are passive; reason is active.

      Through universal concepts reason organizes the senses.

6.   Universals are in God, other rational minds, and particulars.

7.   Prime matter can take any form. It's pure potential.

      Identical twins have the same form; their matter is different.

      This explains how things change, yet have a continuity.
      Water becomes ice.

      The matter we experience is already entangled with form.

8.   God is perfect, fully actualized, simple, immaterial, infinite, timeless, unchanging, and the cause of all things.

      Matter is potential. Form is actuality.

      Things are imperfect because they aren't fully actualized.

      Only one thing can be fully actualized.

9.   God is all good since God is all Being.

      Evil is the lack of being.

10.   An action is good only if the object, circumstances, and end are all good. For example:

      Action - Willing all your money to the church.

      Object - To give your fortune to a needy cause. (good)

      Circumstance - You're dying, and your wife needs the money to support the kids. (bad)

      End - Your intend to buy your way into heaven. (bad)

11.  Good acts are rational, and in accord with the natural law;
      Natural law, objective moral law, is part of our nature.

      Self preservation is part of nature law.

      Is the preservation of offspring a natural law?

      Civil laws are just if they coincide with natural law.

      Civil laws that violate natural law are unjust.

      Unjust laws don't require obedience. (Civil Disobedience)

      Should there be victimless crimes? (See page 201.)

12.  We have an obligation to pursue truth.

13.  The ideal state is a democracy with one ruler whose power is checked.





The question what is the cause of all things presupposes that you cannot have a infinite regress. Each proof agrees with that assumption, and takes the form of Modus Pones:



If A then B

A Therefore B

A > B

A  /  B






1. If change exists, then an unmoved mover exists (God).

2. Change exists.  /  Therefore an unmoved mover exists (God).


1.  C > G

2.  C  /  G



1. If the first premiss is false, an infinite regress is possible.

2. It is not the case that an infinite regress is possible. / Therefore

    It is not the case that first premiss is false.


1.  ~P > I

2.  ~I  /  P

3.  ~~P    1,2 mp

4.  P         3 dn


Would Aquinas agree that everything has a  cause?





1. If contingent things exist, a necessary Being exists (God).

2. Contingent things exist.  / Therefore a necessary Being exists.


1.  C  > N

2.  C  /  N



The existence of a possible contingent thing depends on some other thing. This leads to an infinite regress, but an infinite regress is impossible, so a necessarily existing thing must exist, and we know this to be God.


1. If the first premiss is false, then an infinite regress is possible.

2. It is not the case that an infinite regress is possible. / Therefore

    It is not the case that first premiss is false.


1.  ~P > I

2.  ~I  /  P

3.  ~~P    1,2 mp

4.  P         3 dn





1.  If degrees of perfection exist, then ultimate perfection exists.

2.  Degrees of perfection exist. / Therefore ultimate perfection exists.





The only way we could judge degrees of being, value, or perfection is if ultimate Being, Perfection, and Value served as a reference.




1.  If the world has evidence of design, then God exists.

2. The world has evidence of design. / Therefore God exists.





For Aquinas the world is a teleological; it shows evidence of purpose and design, and that constitutes evidence of God.


Ask yourself this question: What is beauty doing here?




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