AO1: Aquinas’ third way
- Aquinas’ Third Way aims to show a posteriori (from experience) that belief in God can be inductively supported (through evidence) by reason.
- It is based on the modal distinction between contingent and necessary beings.
- P1. We observe that there are contingent beings (things that can possibly not exist).
- P2. If it is possible for something to not exist, then there is some time in which it doesn’t exist.
- C1. If everything were contingent, then at one time nothing existed.
- P3. If nothing once existed, nothing could begin to exist, so nothing would exist now.
- C2. So, there must be something that is not contingent, “having of itself its own necessity … That thing we call God.”
- Aquinas’ focus is on dependence rather than temporal beginnings.
- Contingent beings need an explanation for why they exist.
- He distinguishes between beings that are necessary through another and those necessary through themselves.
- Beings that are necessary through another still depend on something else.
- Even an infinite chain of such beings would not explain why anything exists.
- So there must be a being whose necessity is self-explanatory, grounding all existence.
AO1: The status as a proof of the cosmological argument
- Cosmological arguments are a posteriori, meaning based on experience.
- For example, Aquinas’ ways begin from observing motion, causation and contingency in the world.
- They are typically inductive, meaning their premises could be true while the conclusion is still false.
- The premises support the conclusion but do not guarantee it.
- Such arguments are associated with empiricism, the view that knowledge comes from experience.
- So they cannot establish certainty, but aim to show what we have most reason to believe.
- They are also defeasible, meaning new evidence could overturn them or shift the balance of probability.
- So they can be challenged by rejecting the premises or denying the conclusion follows.
- Cosmological arguments often depend on explanatory principles.
- Leibniz’ Principle of Sufficient Reason claims everything has an explanation.
- Aquinas’ causal principle claims whatever is caused requires a cause.
- Aquinas supports these a posteriori, since we observe causes and explanations in experience, though he treats them as necessary once understood.
- However, applying these principles to the whole of reality is not straightforward.
- They do not by themselves establish the existence of God, and the move to God involves further assumptions.
- So the conclusion is not logically entailed but only probabilistically supported, making the argument inductive.
AO1: Strength & weakness of the cosmological argument AO2 summary
- The fallacy of composition
- Weakness: The fallacy of composition attacks the assumption that the universe as a whole requires an explanation just because its parts do.
- Strength: Cosmological arguments start with what we observe and don’t even mention the universe as a whole, which avoids fallacious part to whole reasoning.
- The im/possibility of an infinite regress
- Strength: An infinite regress may lead to paradoxes regarding infinite library examples and traversing an infinite to get to the current moment.
- Weakness: Scientific models and the lack of empirical evidence undermine claims that an infinite regress is impossible, weakening philosophical arguments against it.
- The brute fact
- Weakness: The possibility of brute facts suggests that not everything requires an explanation, challenging the principle of sufficient reason.
- Strength: The consistent practice of seeking explanations in science and philosophy supports the idea that reality is intelligible and may have an ultimate explanation.
- The Im/possibility of a necessary being
- Weakness: The concept of a necessary being is criticised as logically incoherent, since anything that can be conceived to exist can also be conceived not to exist.
- Strength: Cosmological arguments reference God’s necessity as metaphysical rather than logical, avoiding the ontological argument’s issue of thinking existence is a predicate.
AO2: Hume’s critique of the causal principle
- Hume challenges the causal principle assumed by cosmological arguments.
- He argues it is not analytically true, since we can coherently conceive of an uncaused event without contradiction.
- So it cannot be established through logic.
- Attempts to justify it through experience also fail, because observing causes within the universe does not justify claims about the universe’s origin.
- The only relevant evidence would be observing the universe being created.
- So the causal principle lacks both logical and empirical support.
Counter
- Aquinas’ account of sustaining causation avoids this problem.
- We observe secondary causes which do not have independent causal power.
- Their ability to cause depends on something else sustaining them.
- This creates a hierarchy where causal power must ultimately come from a primary cause.
- A secondary cause without a sustaining cause would be incoherent, since it would have no source of causal power.
- So a causal principle based on sustaining causation can be treated as necessarily true.
Evaluation
- The idea of sustaining causation is not supported by modern science and rests on a controversial metaphysical assumption.
- It claims that causation requires ongoing support from a primary cause, rather than being explained by prior events alone.
- However, physics does not require this type of explanation.
- Theories such as Guth’s inflation model and Krauss’ account of a universe from “nothing” suggest the universe may not need a cause in the traditional sense.
- These accounts challenge the idea that causation must always apply.
- This supports Hume’s view that the universe’s origin could be a unique kind of event.
- So the causal principle is not necessary, and cosmological arguments fail to establish God as its cause.
AO2: The fallacy of composition
- Bertrand Russell argues that what is true of parts need not be true of the whole.
- Just because every human has a mother does not mean the human race has a mother.
- Likewise, even if parts of the universe have causes or are contingent, it does not follow that the universe itself has such an explanation.
- So cosmological arguments risk committing a fallacy of composition.
Counter
- Copleston replies that cosmological arguments do not infer from parts to whole.
- They begin from observed contingent things and argue that the series they form requires explanation.
- Feser notes Aquinas does not refer to the universe as a whole.
- A series of contingent beings cannot be necessary, even if infinite.
- So it still requires an external explanation.
Evaluation
- This response fails because it treats a series as if it were a concrete thing needing its own explanation.
- This is a reification fallacy.
- Hume illustrates this with a collection of particles.
- If each particle is explained, the whole collection is explained.
- There is no extra entity beyond the parts that needs further explanation.
- The same applies to a series of contingent beings.
- A series is just a mental grouping of individual events, not something over and above them.
- In an infinite series, each part can be explained by prior parts.
- So the entire series is explained without needing an external cause.
- Copleston’s argument wrongly assumes the series needs an explanation in itself, aside from its parts.
AO2: The im/possibility of an infinite regress
- Aquinas and Leibniz allow for an infinite regress, arguing that even an infinite series of causes or contingent beings still requires explanation in a primary cause or necessary being.
- Craig strengthens the argument by claiming an actual infinite is impossible.
- He uses examples like an infinite library, where half can equal the whole, creating paradoxes.
- He also argues an infinite past cannot be traversed, so the present could not have been reached.
Counter
- Hume argues there is no contradiction in an infinite regress.
- Scientific models support this possibility.
- Cyclic models suggest an eternal universe without a single infinite timeline, avoiding problems about traversing an infinite.
- Inflation theory proposes a quantum field generating universes, which may be necessary or a brute fact.
- If this exists outside time, then temporal causation and regress do not apply.
Evaluation
- Hume’s approach is more convincing because it respects the limits of philosophical reasoning.
- Craig’s arguments rely on intuitions about infinity and time that may not match physical reality.
- Scientific theories already challenge these intuitions, showing that concepts like time and space behave in unexpected ways.
- Einstein’s remark that time is “what clocks measure” reflects how unclear our understanding still is.
- If modern physics can describe models that avoid these paradoxes, then Craig’s claims lose force.
- Philosophy alone cannot decide what is possible in the physical world.
- So without empirical evidence, the claim that an infinite regress is impossible remains unproven.
AO2: The Im/possibility of a necessary being
- Hume argues that necessity only applies to logical truths, such as “1+1=2”.
- We can imagine anything existing not existing, so the idea of a necessary being is incoherent.
- There is no contradiction in denying the existence of God.
- Russell supports this by claiming necessity is a property of propositions, not things.
- So the claim that “God exists” cannot be necessary in the way cosmological arguments require.
Counter
- Copleston replies that this criticism targets the ontological argument, not cosmological arguments.
- Anselm claimed God’s non-existence is logically impossible, but cosmological arguments use a different idea.
- They claim God is metaphysically necessary as the explanation of contingent reality.
- If the world is contingent, it requires a necessary explanation.
- So God’s necessity is about explaining existence, not logical contradiction.
Evaluation
- Hume’s challenge still succeeds because it undermines the move from necessity to God.
- Even if a necessary being is coherent, it does not follow that it must be God.
- The necessary being could be the universe itself or some fundamental physical reality.
- Modern cosmology supports this possibility, with theories suggesting underlying structures like quantum fields.
- These could explain existence without appealing to a divine being.
- So Copleston’s response shifts the meaning of necessity but does not justify identifying the necessary being with God.
- Cosmological arguments therefore fail to establish a specifically theistic conclusion.