Cosmological Argument incl. Aquinas' First Three Ways

What Is the Cosmological Argument?

The cosmological argument is one of the most important philosophical arguments for God's existence.

The word "cosmological" comes from the Greek kosmos, meaning both "universe" and "order".

The cosmological argument starts from observations about the universe—specifically that things exist, change, and are caused—and reasons backward to the conclusion that God must exist as the ultimate explanation.

The key question: "Why is there something rather than nothing?"

Key Features of Cosmological Arguments

All cosmological arguments share common elements:

1. A Causal Principle: The claim that every event or thing has a cause. Nothing comes from nothing (ex nihilo nihil fit).
2. Denial of Infinite Regress: The claim that you cannot have an infinite chain of causes or explanations without a starting point.
3. A First Cause or Necessary Being: The conclusion that there must be something that is uncaused or necessary—something that explains everything else but doesn't need its own explanation. This is God.

Aquinas' First Way: The Argument from Motion (Change)

Aquinas' First Way is the argument from motion or change.

The Observation:

Everything around us is changing. Things move. Trees grow. Water boils. Objects fall.

For Aquinas, "motion" means any kind of change—a transition from potentiality to actuality.

Examples:

• An acorn is potentially an oak tree, but actually just an acorn. When it grows, it moves from potential to actual
• Wood is potentially on fire, but actually cool. When you light it, it moves from potential to actual
• Water is potentially hot, but actually cold. When you heat it, it moves from potential to actual

The Key Principle:

Nothing can move itself from potentiality to actuality.

Why? Because to cause itself to change, it would have to be both potential and actual at the same time in the same respect—which is impossible.

The wood can't make itself hot. It's only potentially hot. Something actually hot (like a flame) must cause the wood to become actually hot.

Therefore, everything that changes must be changed by something else.

The Logical Structure:

The Analogy:

Aquinas uses the example of a hand moving a stick, which moves a stone.

The stick can't move the stone by itself. The stick only has the power to move because the hand is moving it. Remove the hand, and the stick doesn't move the stone.

Similarly, secondary movers in the universe can only move things because they are themselves being moved by something prior. Ultimately, there must be a primary first mover—something that moves without being moved itself.

This unmoved mover is pure actuality—it has no potential to be anything different. It is completely actual. This is God.

Aquinas' Second Way: The Argument from Efficient Causation

The Second Way is very similar to the First Way, but focuses on causation rather than change.

The Observation:

We observe that things in the world are caused by other things.

For example: Your parents caused you to exist. Their parents caused them to exist. And so on.

The Key Principles:

Why Infinite Regress Is Impossible:

If you remove the first cause, you remove all subsequent causes and effects.

Imagine a chain of dominoes. Each domino falls because the previous one hit it. But if there's no first domino that was pushed, none of the dominoes would fall.

Similarly, if there's no first cause, nothing would exist now.

Important: Sustaining Causation vs. Temporal Causation

This is crucial for understanding Aquinas:

Aquinas is NOT talking about a temporal chain—a sequence of events stretched backward in time.

He's talking about a sustaining causal chain—a hierarchy of causes that exist simultaneously and depend on each other right now.

Example: A hand (first cause) moves a stick (secondary cause) which moves a stone (effect). All three exist at the same time. The stick derives its causal power from the hand. Without the hand, the stick couldn't move the stone.

Aquinas actually thought it was possible for the universe to have existed forever in time. His argument is about the hierarchy of explanation, not about what happened first in time.

Aquinas' Third Way: The Argument from Contingency

The Third Way is the argument from contingency and necessity.

Key Distinction:

• Contingent beings are things that might not have existed. They depend on something else for their existence. Examples: you, trees, planets, everything in nature.
• Necessary beings are things that must exist. They don't depend on anything else. They cannot not exist.

The Logical Structure:

The Core Insight:

If the universe contained only contingent things, there would be no ultimate explanation for why anything exists.

Each contingent thing depends on something else. But the whole collection of contingent things also needs an explanation.

That explanation must be something necessary—something that exists by its own nature and doesn't depend on anything else.

Why These Arguments Are Important

1. They Are A Posteriori: The arguments start from observation of the world, not from abstract concepts. You don't need to accept any religious premises. You just need to observe that things exist, change, and are caused.
2. They Seek Ultimate Explanations: The cosmological argument doesn't just ask "What caused X?" but "What is the ultimate explanation for anything existing at all?". It's about finding a sufficient reason for the universe.
3. They Support Key Attributes of God: The First Cause/Unmoved Mover must be: Uncaused (otherwise it wouldn't be first), Necessary (its existence is not dependent on anything), Unchanging (pure actuality with no potentiality), Eternal (didn't come into being, so has no beginning), Immaterial (material things can change), and Powerful (caused everything else to exist). These are traditional attributes of God.

Major Objections to the Cosmological Argument

1. Hume's Challenge to the Causal Principle

David Hume argued that the causal principle ("everything has a cause") is not a necessary truth. We can conceive of something coming into existence without a cause. Therefore, it's not logically impossible. Maybe the universe just exists without a cause—a brute fact.

Response: William Lane Craig argues the causal principle is metaphysically intuitive. The alternative—that things pop into existence from nothing—seems absurd.

2. Why Can't the Universe Be the Necessary Being?

Why does the necessary being have to be God? Why can't the universe itself be necessary?

Response: The universe appears to be contingent—it's made of contingent parts, it changes, it could have been different. Necessary beings are unchanging and couldn't be otherwise.

3. The Infinite Regress Problem

Maybe there CAN be an infinite chain of causes or contingent beings. Hume argued: if you explain each part of a series, you've explained the whole series. You don't need a separate explanation for the "whole".

Response: Aquinas would say the series itself still needs explanation. Why does this infinite series exist rather than nothing? You still need a necessary being to ground it.

4. The "Who Made God?" Objection

If everything needs a cause, what caused God?

Response: The argument doesn't say "everything needs a cause." It says "everything that begins to exist" or "every contingent thing" needs a cause. God, as a necessary being, doesn't begin to exist and isn't contingent, so doesn't need a cause.

5. Modern Physics and Quantum Mechanics

Some interpretations of quantum mechanics suggest that particles can come into existence uncaused from quantum fluctuations. This might undermine the causal principle.

Response: Even quantum events may not be truly uncaused—they follow probabilistic laws. And quantum fluctuations occur within an existing quantum field, not from absolute nothing.

The Argument's Continuing Relevance

Despite objections, the cosmological argument remains influential:

• It addresses the deep question: "Why is there something rather than nothing?"
• It provides a rational, philosophical case for God without requiring faith
• Modern versions (like the Kalam Cosmological Argument) have been refined and remain debated
• It resonates with the human intuition that existence requires explanation