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Title: History of Philosophy Lecture 12 Thomas Aquinas


1
History of PhilosophyLecture 12Thomas Aquinas
  • By David Kelsey

2
Aquinas
  • Saint Thomas Aquinas
  • Lived from 1225-1274.
  • A monk whose writings have been deemed
    authoritative by the Catholic Church.
  • In 1244 became a friar. Later he became a priest
    and in 1323 was made a Saint.
  • Heavily influenced by the works of Aristotle.
  • In his work Summa Theologica he gave 5 different
    arguments for Gods existence.
  • He called these the 5 ways.

3
Aquinas on Aristotle
  • Aquinas on Aristotle
  • Aquinas was greatly influenced by the works of
    Aristotle.
  • But Aquinas thinks there is a fundamental mistake
    in Aristotles metaphysics.
  • Aquinas thinks Aristotle overlooks the notion of
    existence.
  • Aristotle on existence
  • Form is what actualizes a potentiality, matter,
    into an actually existing thing.
  • And efficient causes are what bring a particular
    substance into being.
  • But the world, existing eternally, has no
    efficient cause. Existence is just born in its
    form.

4
Aquinas on existence
  • So for Aristotle, Form brings existence along
    with it. But for Aquinas, a things existence
    differs from its essence.
  • The essence of any substance is both matter and
    form for such an object is different from
    something purely formal
  • For something imaginary like a phoenix, its
    essence being form and matter, it lacks
    existence.
  • So existence is something added to those
    substances that do in fact exist.
  • Likewise for spiritual substances, they are
    composed of pure form and existence.
  • It is this new understanding of existence which
    leads Aquinas to rethink Aristotles notion of
    efficient causation and subsequently Gods
    existence as unmoved mover.
  • We now turn to Aquinas famous 5 ways

5
Theism
  • There are 3 general argument patterns for Theism.
  • Theism, Atheism Agnosticism
  • We have so far seen one of these argument
    patterns the Ontological argument.
  • Ontological Arguments
  • Argue that by an analysis of the very concept of
    God he must exist.
  • Cosmological Arguments
  • The form of the argument is roughly this
  • There must be a first cause of all things and
    this first cause must be God.
  • Teleological Arguments
  • Argue for Gods existence via premises about the
    design or goals or purposes of things.

6
The 5 ways
  • The 5 ways
  • The first way about things causing change in
    other things.
  • The second way about efficient causation
  • The third way about things causing others to
    exist
  • The fourth way about things causing others to be
    good or noble.
  • The final way about purposes.

7
Aquinas 5 ways
  • The first 4 ways
  • Different versions of the Cosmological argument.
  • Each way uses a different sense of the word
    cause.
  • In each case Aquinas wants to show that there is
    an uncaused cause
  • All Cosmological arguments have a form like this
  • 1. There is something that causes everything
    else, I.e. a first cause.
  • 2. Only God could be a first cause.
  • 3. Thus, there is a God.
  • The final way a version of the teleological
    argument.

8
The first way
  • The form of the first way
  • 1) Things change.
  • 2) Change is an alteration in which something
    becomes actually what it was only potentially
    until then.
  • 3) Everything that changes must be made to change
    by another thing.
  • 4) But if one thing causes change in another,
    either the cause is a first cause of change or it
    is caused to change by another (from 3)
  • 5) There couldnt be an open causal chain of
    changing changers going back forever into the
    past.
  • 6) Thus, there is an unchanging changer, a first
    cause of change. (from 1 5)
  • 7) And this first cause is God.

9
Aquinas argument for the 3rd premise
  • The third premise 3) Everything that changes
    must be changed by another thing.
  • A change from potentiality to actuality can only
    be brought about by something that is already
    actual.
  • The ball and batter
  • Nothing can be both potential and actual in the
    same respect.
  • So nothing can change itself.
  • Thoughts on this argument? Can you think of
    anything that could change itself?

10
Aquinas argument for the 5th premise
  • The 5th premise There couldnt be an open causal
    chain of changing changers going back forever
    into the past.
  • In this case there is no first cause of change
  • Open causal chain an infinite number of things,
    one causing change in the other
  • Ball and Batter
  • But then there couldnt be any intermediate
    causes either
  • Such causes could only cause change if actualized
    themselves by some prior cause.
  • Ball and Batter again
  • But if there werent any intermediate changers
    there would be no change at all.
  • Thoughts on this argument?
  • Is it possible that we have intermediate causes
    of change without a first cause?
  • Maybe there is another possibility a closed loop
    of intermediate changers

11
Evaluating the first way
  • The first premise
  • says simply that things change.
  • Change Aquinas means the kind of change we see
    in the ball when it is hit by the bat.
  • The fourth premise
  • Assuming that everything that changes must be
    changed by another thing, if one thing causes
    change in another, either the cause is a first
    cause of change or it is caused to change by
    another.
  • The fifth premise
  • There is an unchanging changer, a first cause of
    change.
  • This thing isnt changed by anything else. It
    can cause change though.
  • Dominos
  • Question why suppose that there is just one
    unchanging changer?
  • The conclusion
  • This first cause is God
  • Question why suppose this first cause is God?

12
The Second Way
  • The Second way
  • 1) efficient causes come in series
  • Something cannot be the efficient cause of itself
    for to be so it would have to preexist itself,
    which is not possible.
  • And if you take away a cause you take away its
    effect
  • 2) Such series of efficient causes could not go
    on to infinity
  • If the series were infinite there would be no
    first cause.
  • If there were no first cause there would be no
    intermediate causes...
  • 3) So there must be a first efficient cause
  • 4) this everyone gives the name God

13
Evaluating the Second way
  • Challenging the Second way
  • Some things to notice
  • Notice the similarity between the first and
    second ways
  • The second way is focused on a specific kind of
    causation, efficient causation.
  • An efficient cause causes something to come to be
  • Example the hammer, the spark and the explosion
  • Evaluating the premises
  • Premise 1
  • Questions?
  • Premise 2
  • Questions?
  • Premise 3
  • Questions?
  • The conclusion
  • Questions?

14
The Third Way
  • Two ways in which a thing can exist
  • Necessary things cant fail to exist.
  • Contingent things come into and go out of
    existence.
  • The third way
  • 1. Some things must exist of necessity.
  • 2. There cant be an open causal chain of
    necessary things each causing the next to be
    necessary.
  • 3. Thus, something must be necessary per se.
  • 4, And this is God.

15
The first premise
  • The first premise
  • Says that something must be necessary.
  • So not everything can be contingent.
  • His argument
  • 1) consider if everything existed contingently.
  • 2) All contingent things must start to exist at
    some time.
  • 3) So all contingent things must fail to exist at
    some time. (from 2)
  • 4) But then there must have been a time at which
    nothing existed. (from 1 3)
  • 5) But if there had been such a time nothing
    would exist now.
  • From nothing you get nothing
  • 6) But things do exist now.
  • 7) Something must exist of necessity. This thing
    caused contingent things to come to be.

16
Finishing the 3rd way
  • The second premise
  • says that there cannot be an open causal chain of
    necessary things each causing the next to be
    necessary.
  • His argument
  • In this case there is no first cause of change.
  • But then there couldnt be any intermediate
    causes and so no change at all
  • Question?
  • The third premise
  • says that something must be necessary per se
  • Necessary Per Se
  • Something that owes its necessity to nothing
    else
  • it can cause the necessity of other things
    though.
  • Question?
  • The conclusion
  • Questions?

17
The Fourth Way
  • The fourth way
  • 1) Some things are good (noble and true).
  • 2) Some things are better (or more noble or
    truer) than other things.
  • 3) These better (more noble and truer) things
    have more good (are more noble and are truer) in
    accord with their distance from a maximum.
  • Comparative judgments
  • 4) if something that is maximally true, good and
    noble were not in existence then there would be
    no things possessing truth, goodness and nobility
    to a lesser degree.
  • So whatever is maximally good (noble and true) is
    the cause of whatever else that is good
  • 5) Thus, something is maximally good and causes
    everything else that is good (from 1 4)
  • 6) This maximally good thing we call GOD.

18
Finishing the argument
  • Something to notice
  • Notice the appeal that this argument makes to the
    great chain of being
  • The first 3 premises
  • The fourth premise
  • Question This seems to imply that the maximally
    good thing is the cause of whatever else is good.
  • Questions?
  • Premise 5
  • The conclusion

19
The fifth way
  • The fifth way
  • 1) Everything has a design, acts for a purpose.
  • 2) Something can only have a design or act for a
    purpose if it is directed to do so by a designer.
  • Ex arrows and archers
  • 3) Everything has a designer, which we call God.

20
The first premise of the Design Argument
  • The first premise
  • 1) Everything has a design, acts for a purpose.
  • Goal-directed behavior is observed in all natural
    substances
  • Their behavior hardly ever varies and is almost
    always turning out well
  • Just like we plant and harvest and store food for
    the winter, intention and design is pervasive
    throughout
  • Examples...

21
Understanding the fifth way
  • The fifth way
  • is a teleological argument for the existence of
    God.
  • Teleological Arguments
  • Most are arguments by analogy.
  • They usually rest on some analogy between things
    we know to be designed by humans and things we
    know not to be designed by humans, such as the
    universe as a whole.
  • The analogy is then made if the first has a
    designer so does the second, which is God.

22
Thoughts aboutthe fifth way
  • Thoughts about the fifth way?
  • Finding a relevant difference
  • Anyone see a relevant difference?
  • Things vs. universes?
  • Could something besides God be the designer of
    the universe?
  • Other possible designers
  • Gravity?
  • Evolution?
  • Aquinas reply
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