Turtles All the Way Down
If everything has a cause, what caused the first thing? And if something can exist without a cause, why can't that something be the universe itself?
The 'turtles all the way down' image comes from a story, attributed variously to William James, Bertrand Russell, and others, about a cosmologist explaining that the Earth rests on the back of a turtle. When asked what the turtle rests on, the questioner is told: 'It's turtles all the way down.' The regress problem it illustrates is ancient and unresolved.
The regress
Every explanation refers to something prior. Every cause has a prior cause. Tracing things back seems like good epistemic practice. But the chain has to start somewhere, or go back forever. Neither option is comfortable.
The three positions:
- Infinite regress: the chain of causes goes back forever. Nothing is uncaused; the sequence simply has no beginning.
- First cause: something started the chain without itself having a cause, a self-existent foundation. Classical theology names this God. Modern physics names it the Big Bang (though that's a different kind of claim).
- Circular causation: the chain loops back on itself. Some cosmological models in physics explore universes that are, in a sense, causally self-contained.
Why this isn't just a religion question
The regress problem shows up everywhere. Even if physics explains the Big Bang, it doesn't explain why physical laws exist rather than no laws at all. The constants of nature seem fine-tuned, but explaining them by appeal to deeper laws just pushes the question back. And Gödel's incompleteness theorems showed that any mathematical system either has unprovable truths or is inconsistent, meaning foundations can't fully justify themselves.
The pragmatic answer
William James, from whom the turtle story may originate, was a pragmatist. His view: the regress is a real problem, but it's a problem for every worldview, theist, atheist, and physicist alike. Nobody gets a free foundation. The honest move is to notice where your chain of justification stops and own it.