Everything is undefined.

You may disagree. “Everything” is defined in the dictionary, after all. But there is a problem: words in the dictionary are all defined in terms of other words in the dictionary. If you want to know what “everything” is, you’ll first need to know what “the” and “a” are, which in turn depend on other words in the dictionary, and so on. Eventually you’ll get back to “everything.” That’s the infinite curiosity loop.

Of course, this is hardly a problem. We all know what the word “everything” means without looking it up in the dictionary. We learned it from experience. As long all the words we want to look up are defined in terms of some basic words we know from experience, we won’t be stuck in the infinite curiosity loop. Those basic words are curiosity halters.