What other assumption can you start with?

Assuming the natural world is dumb is simple, consistent, and easy to explain.

If you start with the assumption the natural world is “smart”, what does that even mean? Does it mean that we should assume dog can do calculus, but choose not to? Or that dogs are capable of complex communication, but also choose not to?

Saying the natural world is “smart” is a pretty meaningless statement. How smart is “smart”, everyone will have a different opinion, so you can’t use it as the basis for discovery or discussion.

However everyone understands what the natural world being dumb means. From there you can start the journey of proving step-by-step where the smarts are.