Do you consider the words "entirely natural" to be scientific in nature? I consider them to be an arbitrary semantic distinction, the reality of which depends upon the one who employs them, and little more. Fact is, science does not yet know what causes gravity, so bag it for a better day.
I know! I know! It's the Intelligent Puller! That's much better than General Relativity or Quantum Theory, so we can forget those. After all, they don't explain everything, but Intelligent Puller Theory does.
You don't believe? Drop a book. You saw it drop. Therefore, the Intelligent Puller must have pulled it towards the ground.