Some people say that nothing is evil and everything has a purpose.  Even fleas, ticks, rats and other vermin serve a purpose, we just are not smart enough to know what it is.  This is based on the idea that God created everything in the physical world and God would not create something that is all evil and has no purpose.      
    As Gnostics, we have a different point of view.  We say that the physical world was created by the fallen angels, the demerge.  As such, it is a flawed world, an imperfect world.  A fun house mirror copy of the spiritual world with everything distorted, often beyond recognition.  Creatures created from our own dreams and nightmares like in the classic science fiction movie "Forbidden Planet ".  Do you think there are fleas in heaven?  If not, than why would God put them here?  
    We don't even agree that everything in the material world has a purpose.  It is true that sometimes the purpose of something isn't obvious and sometimes, sadly, we only discover how important some plant or animal really is after it becomes extinct, but just because some things have a hidden purpose, doesn't mean everything does.  I do agree with the well-known yin-yang symbol of the material world that nothing is totally one or the other, totally male, or female, hot or cold, good or evil, but that doesn't mean that deep down everything is really good, we just don't know why.