Here's the fuller quote:

>If only it were all so simple! If only there were evil people somewhere insidiously committing evil deeds, and it were necessary only to separate them from the rest of us and destroy them. But the line dividing good and evil cuts through the heart of every human being. And who is willing to destroy a piece of his own heart?

And another, similar one:

>It was granted me to carry away from my prison years on my bent back, which nearly broke beneath its load, this essential experience: how a human being becomes evil and how good…Gradually it was disclosed to me that the line separating good and evil passes not through states, nor between classes, nor between political parties either—but right through every human heart—and through all human hearts. This line shifts. Inside us, it oscillates with the years. And even within hearts overwhelmed by evil, one small bridgehead of good is retained. And even in the best of all hearts, there remains… an unuprooted small corner of evil.

Both quotes are from his book Gulag Archipelago