You can think of "acting on the world" as resolving questions about the world, like "what happens when I do X"? You could observe the results of others acting,

You can think of "acting on the world" as resolving questions about the world, like "what happens when I do X"? You could observe the results of others acting, but it means that the questions you're getting answers to are outside of your control. So if you need to know the answer to a particular question, you either need to test it yourself, or hope that whoever you're watching will test it for you.