The Cosmological Argument


The Cosmological Argument

Aquinas' Way 3- the argument from contingency and necessity.

Aquinas' argument is a posteriori- it is empirical in nature and is based on sense experience.

Inductive- based on the probability and not on proof. The stronger the evidence for them, the more likely they are to be true.

Aquinas' Way 3 focuses on contingency and necessity:

  • everything in the cosmos is contingent- this universe of space and time.
  • something must therefore exist necessarily as its cause.
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The Cosmological Argument

Aquinas' Way 3:

Aquinas' version of the Cosmological Argument comes in the first three of his 'Five Ways' which are arguments intended to prove the existence of God.

There are two parts to this argument;


  • because everything in the natural world is contingent, there must have been a time when nothing existed 'out of nothing, nothing can come'.This is ridiculous because vast numbers of contingent things now exist. 
  • so that means that something must exist necessarily.


  • everything that is necessary must be caused or uncaused. Aquinas refers to the possibility of infinite regress (an unending series) of caused necessary beings e.g. angels. But this also is rediculous because then there would be no ultimate cause of the series and so no series at all.
  • so there must be an uncaused necessary being responsible for the existence of all caused necessary beings and all contingent beings.
  • 'This all men speak of as God' Aquinas, Summa Theologica.
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The Cosmological Argument

Criticisms: Hume and Russell:

1) Russell argued that Aquinas was guilty of the fallacy of composition.

  • what is true of the parts is not necessarily true of the whole.
  • just because what we see in the world is caused, it does not mean that the universe itself has a cause.

2) Hume and Russell rejected the concept of a necessary being.

  • statements about existence are synthetic (based on the senses) rather than analytic (based on logic).
  • there is no contradiction in stating that God does not exist.

3) Hume suggested that the universe might be a necessarily- existent being.

  • this logic conforms to Occam's Razor- the rule that if there are competing theories, the simpler one is the better. The conclusion is most likely if it requires fewer assumptions. That is to say, the universe could be necessarily existent rather than contingent upon an unseen, necessarily- existent God.
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The Cosmological Argument

4) Russell took a different approach, claiming that the existence of the universe is simply unexplainable, it is just a brute fact- a fact that has and needs no explanation.

5) Hume argued for the possibility of infinite regress- an indefinite sequence of causes or beings which does not have a first member of the series. It can reasonably be asked what caused God.

6) Hume argued that nothing can be said about the nature of God as a necesarrily- existent being.

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The Cosmological Argument

Evaluation of Aquinas's Way 3:

Weaknesses and their counter arguments;

  • fallacy of composition- what is true of the parts may not be true of the whole. This is not always the case e.g. each of the 50 states of the USA is in the northern hemisphere. The USA is in the northern hemisphere. The second statement is not false.
  • the universe could be a necessarily- existent being. This is supported by the principle conservation of matter and by some modern cosmological theories. The case for necessarily- existing matter is no stronger than that for a necessary- existing mind. Scientific cosmological theories do not explain why there is something rather than nothing, whereas the idea of God does.
  • the universe could be just brute fact. Most people seek an explanation for things and this is how science operates.
  • why not infinite regress of contingent beings? This still does not explaim why there is something rather than nothing. There is no evidence for the existence of an infinite past sequence in the real world, although mathematics contains this idea.
  • it cannot be shwon that the existence of any being is logically necessary. Hume misunderstood Aquinas. Aquinas was talking about God's metaphysical (not his logical) necessity.
  • why just one necessary being? Application of Occam's Razor supports the idea of a single being.
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The Ontological Argument

The status of Aquinas' Way 3 as a proof:

Proof of the existence of God;

  • only deductive arguments can give absolute proof. The Cosmological Argument is inductive so can never be absolutely certain.
  • Aquinas' Way 3 will never convince atheists.

Not prood of the existence of God;

  • most things that we accept as true in life are based on inductive arguments. The stronger the evidence, the more probably true a claim is. Science adopts this approach with the existence of quarks- elementary particles assumed to be one of the building blocks of matter. for which there is no direct evidence but for which there is very strong indirect evidence. If there is the need for a satisfactory explanation of the universe, the Cosmological Argument might be said to provide it.
  • thiw may be true but it may be that no argument, however rational, would convince those whose view of the world is fixed. For a theist, Way 3 might seen to give a reasoned proof of God as the necessary uncaused cause.
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The Cosmological Argument

The value of Aquinas' Way 3 for religious faith:

On the positive side;

  • a reasonable hypothesis. Alternative explanations for the origin of the universe have no greater probability.
  • difficult language, but the concept is easy to understand. The idea is accessible to any Christian and not just to theologians.
  • supported by the Design Argument.

On the negative side;

not all theists accept it;

  • Kant rejected it because he thought the idea of God as a necessary being was dependent on the Ontological Argument.
  • Karl Barth rejected all attempts to prove God's existence through reason.
  • Aquinas did not think it was sufficient on its own. 
  • Faith is supported by reason but natural theology cannot give knowledge of doctrines such as the Trinity.
  • These doctrines are revealed in the Bible and in the teachings of the Church.
  • faith is a gift of God's grace that enables believers to understand them.
  • the theist Stephen Evans regards the argument as having limited value because it does not indicate the God of Christian theism.
  • he saw it as at best pointing to a deist God.
  • Gerry Hughes has reservations about it for the same reason.
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