My friend, Hillary, and I used to have interesting discussions. I miss him for that. A few months before he suffered a stroke and died he asked me what I thought the nature of evil was. As was our custom, I didn't give him an answer right away but took time to compile in my head what I thought the most productive response(s) would be - he was ever a teacher and practiced his own form of the Socratic method - and I'd get back to him with my thoughts.
I loved his challenging questions (everything from simple maths curiosities to profound questions as above) but the point was not to give definitive answers really but to have excellent conversations while exploring the logical and human consequences of some particular stream of thought.
The natures of good and evil are not questions affable to pat answers (classic Hillary to ask questions with depth). My approach to the question had to start from the simple and somewheres in the conversation insights could be gotten. So I came to him with a statement that the nature of evil arises from free will, and is a consequence (whatever it is) of making a choice with limited ethical consideration (willfully or not).
Hillary was extremely well-read and would write addages in Latin, I think less to showoff than to wait quietly for questions to be asked. At some point in our discussion on the nature of evil he brought up the name of the great Christian theologian, Augustine, who said that the roots of evil do not come from the corporeal world, contrary to what fundamentalists believe. Rather he believed the world was the creation of God and therefore not evil in and of itself but perfect as is. Augustine said that evil arises as a consequence of humanity's free will (or more precisely, the misuse of it).
I was raised as a Christian but most of the sense of being Christian was based on emotions of fear-mongering, ignorance and passivity, that destiny was writ and determined even before I was born, that the physical world was evil. Though I'm not religious per se, following Augustine's logic, the Gospels and the book of Revelation seem to make much more sense - that ignorance and selfish ego motives breed evil and whose consequences everyone suffers (the culpable and the innocent alike). Evil has an inherent need to hide itself as it gestates and requires ignorance and passivity to gain and maintain power.
In this age of information, awareness and education have for the first time in human history an opportunity to respond to evil. The great political unrest in North Africa and the Middle East have shown us how pathetic evil really is, and how dangerous it can be welding its apparent double-bind of economic-, political- and personal- self interests at us all. The particular question of "at what cost?" forces us to make hard choices but these are our choices to make. The way out of the double-bind is to realize we must actively make our choices, hopefully as best informed as possible.
As an individual, I've really enjoy getting drunk or stoned or drunk and stoned and its promises of personal oblivion. But I know the consequences of my selfishness. It's a road I've chosen now not to take. Being mature never promised easy, but it's a choice. So far I'm happy and willing to accept my commitment to self control and the choices I've made to live beyond my ego desires. It is hard but mature as I have ever been. Outside of it is alienation from loved ones, homelessness, and the apparently inescapble trappings of guilt.
I must also maintain humility, being human and fragile...