Anagnorisis

I was actually thinking a lot about this theme in Aristotle's Poetics. What makes human beings the top species on Earth? Apart from our opposable thumbs, the characteristic that sets us apart from other animals, is our judgement. We are able to distinguish right from wrong (with the exception of sociopaths). Whether we choose to do right over wrong is something else, but as far as having that ability, we do. If we didn't we would live in anarchy, and we wouldn't have any morals. Animals are much different. If an animal must kill to survive, then that is the nature of things and that is how things go. At no point does a lioness leave a caribou alone because it just isn't nice to rip another animals limb by limb.
This ties into anagnorisis. This recognition that we've done something wrong is only natural and for this reason I believe Aristotle brings up this theme. Many of us can relate to realizing a mistake we've made and, for most of us, eventually changing it (peripetia) or cleansing ourself of what we've done (catharsis). Themes such as these help the audience relate to the characters and once that relationship is made we will be more interested in the work.