Thomas%20Aquinas

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Thomas Aquinas
1225 1274 (Aquinas notes created by Kevin
Vallier)

• Dominican monk, born to Italian nobility.
• Worked 150 years after Anselm.
• Student of Albert the Great
• Studied and commented upon much of Aristotles
  works soon after their translation into Latin in
  western Europe
• Studied important Islamic philosophers including
  Avicenna and Averroes, who themselves were
  heavily influenced by Aristotle

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Rejection of the Ontological Argument
Granted that everyone understands that by this
word God is signified something than which
nothing greater can be thought, nevertheless, it
does not therefore follow that he understands
that what the word signifies exists actually, but
only that it exists mentally. Nor can it be
argued that it actually exists, unless it be
admitted that there actually exists something
than which nothing greater can be thought.
(Summa Theologica I.II.I)
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• Anselms argument rests on his definition of god
  as that which nothing greater can be conceived.
• Aquinas rejects the a priori Ontological
  argument on the grounds that a words meaning
  cannot alone establish the existence of that to
  which the word refers.
• Rather, Aquinas requires existence proofs be
  empirical/ a posteriori, ie. to require
  observational evidence.

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Cosmological Proofs for the Existence of God

1. Cosmology the empirical study of the universe
   considered as a whole system
2. Eg, Hubbles (1929) discovery that the universe
   is expanding rather than in a steady or static
   state
3. Eg, Einsteins (1915) identification of gravity
   the curvature of space/time
4. Eg, The big bang theory of the origin of the
   universe

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Cosmological Proofs for the Existence of God

• A cosmological proof for the existence of God
  derives Gods existence from facts established by
  cosmology
• Form of a cosmological argument
• By observation of the universe or parts of the
  universe we know a posteriori that the universe
  or parts thereof have property P
• The best explanation of P is the hypothesis that
  God exists.
• Therefore, God does exist

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Aquinas Five Cosmological Arguments for Gods
Existence

• Argument from motion
• Argument from efficient causation
• Argument from possibility and necessity
• Argument from gradation
• Argument from governance

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Argument from motion

• There is motion.
• Motion involves the reduction from potentiality
  to actuality. (eg an activated spring on the
  garden gate)
• So all motion was first potentiality.
• Only what is actualized in some regard can reduce
  something from potentiality to actuality in that
  regard. (eg, the squirrel that releases the
  coiled spring on the gate)
• Nothing can reduce itself from potentiality to
  actuality.
• Nothing can move itself.
• There cannot be an infinite sequence of movers.
• ? There must be an unmoved prime mover, i.e.
  God.

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Argument from efficient causation

1. The sensible world is full of the effects of
   efficient causation.
2. Nothing can be an efficient cause of itself.
3. If a things cause is absent, then it cannot
   exist.
4. Efficient causes are ordered 1st -gt intermediate
   -gt (ultimate) effect.
5. So without a first cause, there cannot be
   (ultimate) effects.
6. ? So there must be a first efficient cause,
   i.e. God.

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Problems with cosmological arguments

• The arguments from motion and efficient causation
  deny that anything can move or cause itself
  except God. However, what establishes this
  exception? Rather, why should we not simply say
  that the sequence of causes/movers is
  historically infinite?
• Also, Aquinas arguments do not demonstrate that
• a single thing is responsible
• the first cause in any way resembles the
  Judeo-Christian god
• the thing responsible still exists

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Argument from contingency and necessity

1. Some natural things exist contingently.
2. For each contingent thing, there is a time at
   which it does not exist.
3. If everything were contingent there would be a
   time in the past when nothing existed.
4. If there were such a time, then nothing would now
   exist.
5. ? So, something must exist that is not
   contingent but rather necessary and which gives
   rise to all things. This necessary being is God.

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Problems with the contingency argument

• Even if each particular object in the history of
  the universe exists contingently, it does not
  follow that there must be a time when no
  contingent objects exist.

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Argument from gradation

1. Everything is comparable /commensurable with
   respect to value and being.
2. There is a gradation in these properties,
   especially value. That is, some things are
   better than others.
3. One thing is better than another only if the
   former is more similar to that which is perfect
   than is the later.
4. So, since things are comparable with respect to
   value, there must exist that which is perfect,
   and this can only be God.

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Problem with gradation

1. The third premise is critical to the argument.
   However, this premise is dubious. What reason
   secures that variation in value presupposes the
   existence of the standard of perfection? Notice
   that there are many examples of comparability
   that do not presuppose the existence of the
   relevant standard e.g. one thing can be taller
   than another without it being the case that there
   exists any (third) object on which the comparison
   depends.

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Argument from governance

1. Some natural unintelligent objects have purposes.
   (E.g. the purpose of the heart is to pump blood
   the purpose of the wing is to enable flight.)
2. Purpose is always the result of intelligence.
3. The purpose of some natural unintelligent objects
   was not established by any natural intelligent
   being (such as a human).
4. ? So, there must be a supernatural intelligent
   being responsible for such purpose, and this is
   God.

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Problems with governance

• Is it correct that objects have purposes in the
  sense required by the argument?
• If objects do have purposes in the sense required
  by the argument, might these purposes not be
  established simply by the unintelligent processes
  of evolutionary biology?