The cosmological argument claims that features of the universe, such as causation, change, or contingency, require an ultimate explanation identified as God. It is an a posteriori argument because it begins with observations about the world rather than definition or pure reason alone.
The argument generally follows this structure:
- The universe contains dependent things, causes, or changes.
- These cannot provide a complete explanation for their own existence.
- An infinite regress of dependent explanations is rejected as insufficient or impossible.
- Therefore, reality requires a first cause or necessary being that does not depend on anything else.
- This ultimate explanation is identified as God.
Several versions develop this reasoning differently:
| Version | Core reasoning |
|---|---|
| Aquinas's arguments | Motion, efficient causation, and contingency require a first mover, first cause, or necessary being. |
| Kalam cosmological argument | Whatever begins to exist has a cause; the universe began to exist; therefore, the universe has a cause. |
| Leibniz's argument | The principle of sufficient reason requires an adequate explanation for why contingent reality exists rather than nothing. |
A major objection is that rejecting an infinite regress does not automatically prove the existence of the God of classical theism. Even if there is a first cause, further argument is needed to show that it is personal, omnipotent, omniscient, and perfectly good.
Another objection asks, "Who caused God?" Defenders reply that this misunderstands the conclusion: God is proposed as necessary, not contingent, and therefore does not begin to exist or require an external cause. Critics may respond that treating God as necessary is unsupported or that the universe itself could be the unexplained foundation.
A common misconception is that every cosmological argument says, "Everything has a cause." Most versions claim only that things which begin to exist, change, or exist contingently require explanation.
For an IB Philosophy response, clearly reconstruct one version as premises and a conclusion, then evaluate whether its assumptions justify both a first cause and the attributes traditionally assigned to God.
