Agoustin's theory about the problem of evil and it's critiqe from Avecina's view

The problem of evil is one of the most important philosophical problem that it show in different ways and it criticize to religious teachings. Augustine and Avicenna to overcome on the problem of evil used from solution of non-existence evil. But can this solution include all manifestations of evil? non-existence evil’s theory of Avicenna, solve some instances of evil and he uses from the best system for perceptual evil. Augustine's theory because of say all evils are non-existence and he refers all of them to "sin", is unrealistic and it have internal conflict. Avicenna's theory seems more success in solve the problem of evil because he uses from different solutions.