Proverbs 26:11 says, "As a dog returns to his vomit, so a fool repeats his folly." Why does a dog return to his vomit? To lick it up, right? But why do they do this? The best answer I can find so far is because it's in their nature. But why is it in their nature? Is it part of their returning to health, by ingesting what their bodies originally rejected, and thus building up immunity? Or does it have something to do with territorial instincts, so that other dogs or predators will not know they are weak when they find that they have vomited? Or something else?