Transcript Aquinas on the existence of God - People at Creighton University

Aquinas on the existence of God
Aquinas’s arguments for God
 Aquinas’s famous 5 arguments appear in
both the Summa Theologica & the
Summa Contra Gentiles
 Will examine arguments 2 & 5 only
 Aquinas’s approach in all of the
arguments
Aquinas on the existence of God ~ slide 1
Aquinas on the existence of God
God’s existence can be known
through God’s effects, i.e, the
created world (SCG, chapter 12)
 The 2nd argument
1. We experience causality.
2. Nothing is the cause of itself;
causes are other than their effects.
Aquinas on the existence of God ~ slide 2
Aquinas on the existence of God
3. There cannot be an infinite
regress of caused causes.
 If there were an infinite
regress, the effects we
experience here & now would
not exist.
4. Therefore, there must be some
first cause and this we call “God.”
Aquinas on the existence of God ~ slide 3
Aquinas on the existence of God
 Critique
Clarification: a temporal series of
causes vs a dependent series. Aquinas
is talking about a dependent series.
Can’t we take the observed causality
in the world as a brute fact which
requires no explanation?
Aquinas on the existence of God ~ slide 4
Aquinas on the existence of God
Possible response: If we accept the
Principle of Sufficient Reason, then
causality must have an explanation.
 Why should we accept the P. of
SR?
 Because it is a necessary condition
for rationality?
Aquinas on the existence of God ~ slide 5
Aquinas on the existence of God
Richard Swinburne (The Existence of
God, 2nd ed. rev., Oxford UP, 1991)
proposes redoing Aquinas’s 2nd
argument
 God is necessary to account for
the existence of & the sustaining
of the laws of nature which in turn
govern the causality we
experience.
Aquinas on the existence of God ~ slide 6
Aquinas on the existence of God
 God
 laws
 causal events
Aquinas on the existence of God ~ slide 7
Aquinas on the existence of God
The 5th argument
 1. The experiential datum: things which
lack knowledge act toward ends (goals).
 Nature displays goal-directedness;
it is purpose-filled.
 2. Things which move toward ends must
be guided by an intelligence.
 Analogy to an arrow shot by an
archer.
Aquinas on the existence of God ~ slide 8
Aquinas on the existence of God
 3. Therefore, there must exist an
intelligent being who directs all noncognitive natural things toward their
goals. “And this we call God.”
Aquinas on the existence of God ~ slide 9
Paley’s version of the design argument
In the 19th century, William Paley (17431805) in his Natural Theology; or Evidences
of the Existence and Attributes of the
Deity (1802), redid Aquinas’s argument.
 Observing a stone & finding a watch
 I find that it has a purpose & all of its
parts have a purpose.
 The watch must have a watchmaker, a
intelligent designer.
Aquinas on the existence of God ~ slide 10
Paley’s version of the design argument
It does not matter if somehow the
watch was made by a previous watch &
that by a previous, etc. This would
only increase our admiration for the
watch.
And it does not matter that we have
never seen a watch made. Cf. finding
a piece of ancient art.
Aquinas on the existence of God ~ slide 11
Paley’s version of the design argument
Concludes that there must be a
“designing mind” behind the watch, or
watches.
Now the design we observe in the
watch exists in nature, but to an even
greater degree.
Aquinas on the existence of God ~ slide 12
Paley’s version of the design argument
“The contrivances of nature surpass
the contrivances of art, in the
complexity, subtlety, and curiosity of
the mechanism.” “And still more . . .
do they go beyond them in number and
variety.”
 Conclusion: Nature must have a
designer and this is God.
Aquinas on the existence of God ~ slide 13
Aquinas on the existence of God
Critique of the design argument
 The challenge of Darwin’s theory to all
design arguments based on the design
of living things
The theory of natural selection
 (1) Overproduction of pollen,
seeds, eggs, & sperm; yet
populations remain relatively
constant.
Aquinas on the existence of God ~ slide 14
Aquinas on the existence of God
 (2) There is a high mortality
 (3) Individuals within a species
are not identical; there are some
variations.
 (4) Some of these variations are
inheritable.
 (5) Some individuals are better
adapted than others to the
conditions of life and to ecological
niches.
Aquinas on the existence of God ~ slide 15
Aquinas on the existence of God
 (6) Because of (5), there is
natural selection & differential
survival.
 (7) Over the long run, (6) results
in the rise of divergent stocks
issuing from common ancestors.
Darwin’s theory offers a natural
explanation for the design of living
things. Hence there is no need to
appeal to God for this design.
Aquinas on the existence of God ~ slide 16
Aquinas on the existence of God
Responses:
 Can reconcile God with the natural
evolution of the design of living
things by stating that God uses
evolution to bring about this
design.
 But note that this is not an
argument for God’s existence;
it is a statement of the
compatibility of God the
designer and evolution.
Aquinas on the existence of God ~ slide 17
Aquinas on the existence of God
Responses (cont’d)
 Swinburne: God is required to
explain the existence and
sustaining of the laws governing
the evolutionary process.
Aquinas on the existence of God ~ slide 18
Aquinas on the existence of God
 Darwin’s theory is restricted to
the realm of life. Some claim we
need God to explain the evolution
of the cosmos from the Big Bang.
 The cosmos displays
remarkable fine-tuning
directed toward the creation
of life and mind. This can only
be explained by the existence
of an intelligent designer.
Aquinas on the existence of God ~ slide 19