This is an excerpt from Dostoevsky's The Brothers Karamazov. It is a dialogue between Alyosha and Ivan Karamazov (although Ivan does the majority of the talking, Alyosha does interject periodically).
Also worth noting is that this is the Garnett translation; if you're interested in reading any of Dostoevsky's work, I'd recommend reading this as a litmus test for Garnett's style. If you don't like him, you can sample some of the P&V translation to see if you prefer it over Garnett.
Looking forward to hearing what you guys think of the excerpt and the problem of evil!