Aquinas Proofs

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GOD AND PHILOSOPHY
CAN WE PROVE GODS EXISTENCE?
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ONTOLOGICAL MEANS

• relating to or based upon being or existence
• Main Entry ontology 1 a branch of
  metaphysical philosophy concerned with the nature
  and relations of being2 a particular theory
  about the nature of being or the kinds of
  existents

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• metaphysical
• 1 of or relating to metaphysics
• Traditionally, metaphysics refers to the branch
  of philosophy that attempts to understand the
  fundamental nature of all reality, whether
  visible or invisible. It seeks a description so
  basic, so essentially simple, so all-inclusive
  that it applies to everything, whether divine or
  human or anything else. It attempts to tell what
  anything must be like in order to be at all.
• "Meta" in Greek means over, and --- since when
  you jump over something you find yourself behind
  or after it --- it is also understood as behind
  and after.

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• The word "metaphysics" is said to originate from
  the mere fact that the corresponding part of
  Aristotle's work was positioned right after the
  part called "physics".
• But it is not unlikely that the term won a ready
  acceptance as denoting this part of philosophy
  because it conveyed the purpose of metaphysics,
  which is to reach beyond nature (physis) as we
  perceive it, and to discover the "true nature" of
  things, their ultimate essence and the reason for
  being.

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Anselm of Canterbury(1033-1109 AD)
The Ontological Argument for the Existence of God
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Italian nobility. Became a Benedictine
monk Studied under and succeeded Lanfranc as
abbot. Archbishop of Canterbury. Theological
writer. Counselor to Pope Gregory VII, Pope
Urban II, and William the Conqueror. Opposed
slavery and obtained English legislation
prohibiting the sale of men. Exiled by Kings
twice in his lifetime for defending the
truth. One of the great philosophers and
theologians of the middle ages. Doctor of the
Church
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What is the ontological reference of the word
God?
That is, what kind of being does the word God
refer to? According to Anselm, the word God
refers to something than which nothing greater
can be thought of.
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Anselms 1st ontological argument
Something than which nothing greater can be
thought of cannot exist only as an idea in the
mind because, in addition to existing as an idea
in the mind, it can also be thought of as
existing in reality, that is, objectively, which
is greater than existing only as an idea in the
mind. If something than which nothing greater
can be thought of exists only as an idea in the
mind, then that than which something greater
cannot be thought of is that than which
something greater can be thought of, which is
impossible because it is self-contradictory. Some
thing than which nothing greater can be thought
of must exist, not only as an idea in the mind,
but in reality.
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In other words,
A God that actually exists is greater than a
God that exists only as an idea in the mind. If
God exists only as an idea in the mind, then
God is not-God (because something that exists
only as an idea in the mind is not something
than which nothing greater can be thought
of). Thus, the claim that God does not actually
exist implies a contradiction and is therefore
necessarily false. If the claim that God does not
actually exist is necessarily false, then the
claim that God actually exists is necessarily
true (because the negation of a contradiction is
a tautology).
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Anselms 2nd Ontological Argument
It is possible to think of something that cannot
be thought not to exist that is, a necessary
being. A necessary being something that cannot
be thought not to exist would be greater than
something that can be thought not to exist that
is, a contingent being. If something than which
nothing greater can be thought of could be
thought of as not existing, then something than
which nothing greater can be thought of would not
be something than which nothing greater can be
thought of, which is an outright contradiction
and thus absurd. Something than which nothing
greater can be thought of has such a high degree
of existence, that is, necessary existence, that
it cannot be thought of as not existing, that is,
its nonexistence is impossible.
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In other words,

• It is possible to think of a necessary being,
  i.e., a being whose nonexistence is impossible.
• Necessary existence is greater than contingent
  existence, and a necessary being is greater than
  a contingent being.
• If the nonexistence of God is possible, then God
  must be a contingent being. But then God would
  be not-God because a contingent being cannot be
  something than which nothing greater can be
  thought of.
• Thus, the claim that Gods nonexistence is
  possible implies a contradiction and is therefore
  necessarily false.
• If the claim that Gods nonexistence is possible
  is necessarily false, then the claim that Gods
  nonexistence is impossible is necessarily true
  (because the negation of a contradiction is a
  tautology).

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MORE THAN 150 YEARS LATER
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Aquinas Proofs

• The five ways

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Thomas Aquinas (1225-1274)

• Joined Dominican order against the wishes of his
  family led peripatetic existence thereafter.
• Considered the most learned man of his day much
  in demand as teacher and lecturer.
• Summa Theologica never finished, following
  ecstasy in Dec. 1273
• Doctor of the Church

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Aquinas on Gods existence

• Believed, as against several interesting
  objections, that Gods existence can (and needs
  to be) demonstrated (proved, in the modern
  sense).
• By this he meant 2 things
• 1. That God exists is not self-evident or
  axiomatic or a matter of definition
• 2. That God exists is something which we can be
  completely sure of, as a matter of reason (and
  not simply of faith)

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Is the existence of God self-evident?

• self-evident that which requires no proof in
  order to be known.
• 3 objections the existence of God is
  self-evident because
• I. Knowledge of God is innate
• II. The concept includes existence
• III. God is truth, no one can consistently
  deny the existence of truth.

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Answers to the objections

• Objection 1 we know only in a vague way (God is
  mans beatitude) that God exists, and this is
  quite different from knowing absolutely that He
  exists.
• Obj.2 distinction between mental and real
  existence maintained even in the case of that
  than which no greater can be thought
• Obj.3 The existence of truth in general is
  self-evident but the existence of a Primal Truth
  is not self-evident to us.
• General rejoinder what is self-evident cannot be
  denied, but God is can be denied.
• Therefore, God is is not self-evident (that is,
  his existence requires proof)

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Objections to the idea that Gods existence can
be proven

• Objection 1 Gods existence is a matter of
  faith, not demonstration (reason)
• Obj. 2 God, by definition, exceeds our
  understanding, therefore we cant even know what
  it is were trying to prove the existence of
  (the essence is the middle term of
  demonstration)
• Obj.3 We cant know God directly, only by his
  effects but His effects (as finite objects or
  events) cant tell us anything about His nature
  (which is, by dfn., infinite). Therefore, we
  cant prove anything about Him.

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Replies to the objections

• Objection 1 Anything which can be known by
  natural reason is not an article of faith --
  something is an article of faith only if it
  cannot be known by other means
• Obj.2 We dont need to know what it is that
  were proving the existence of (that is, its
  essence), only that it exists
• Obj.3 As in 2, were only trying to prove that
  He exists and not anything about His nature.
  Every effect indicates, at the very least, the
  existence of its cause.
• General rejoinder 2 ways of proving things a
  priori and a posteriori Gods existence can only
  be proven in the latter way

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Character of Aquinas proofs

• Aquinas distinguishes a priori (from cause to
  effect from the nature of something to its
  consequences) from a posteriori (from effect to
  cause from observable consequences to the nature
  of what causes those) proofs -- the first are
  deductive proofs, what are the second kind? Are
  they proofs at all? (recall our previous
  discussion of proof?)

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Proof 1 argument from motion

• motion Aquinas understands to be a paradigm
  case of change the argument here is better
  thought of as the argument from change
• Change going from potential to actual
• Every such move requires something which is
  itself actual to begin with
• A chain of such moves cannot be infinitely long
• Therefore, there must be a first mover (a first
  initiator of change), which is not itself moved
  this first mover is God.

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Proof 2 argument from efficient cause

• Aquinas, following Aristotle, recognizes four
  kinds of causes (4 kinds of why) formal,
  material, final, and efficient causes
• Nothing is the efficient cause of itself
  therefore, for every effect there must exist some
  efficient cause distinct from the effect
• Such a chain of causes cannot go on to infinity
  therefore there is a first cause (and that is God)

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Proof 3 argument from possibility

• Everything which exists, exists only contingently
  (that is, it is possible that it could not exist)
• Any contingent being must have, at some time, not
  existed (if it is possible that it not exist at
  this time, then necessarily it did not exist at
  some time)
• The world, taken as a whole as contingent, must
  have at some time therefore not existed
• But what once did not exist must come to exist in
  virtue of something which itself must exist.
• That necessary being is God.

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Proof 4 argument from gradation

• Every quality or attribute which can be thought
  of in terms of degree, is referenced to some
  standard (more or less good to some standard of
  goodness, more or less red to some standard of
  redness, etc.)
• Since being admits of degrees (as does goodness
  every other sort of perfection), there must be
  something which is the standard for that
  attribute (a formal cause of that attribute)
• That standard is God

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Proof 5 argument from design

• Natural kinds and events are only understood
  properly as having an end state or aim
• Such non-intelligent things can act towards such
  ends only by being directed by something which is
  intelligent (something which could have motives
  or purposes)
• Therefore there is an intelligent being which
  directs natural kinds and events and that being
  is God.

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Character of Aquinas God

• What is the nature of the God which is revealed
  by the five ways?
• the initiator of all motion (change)
• the ultimate cause of all things
• a necessary being
• the standard against which all things are
  measured
• a surpassingly complex intelligence