A bit of a quiz

Since I’m bored and I came across this excerpt taken from a novel which I think is absolutely brilliant. I would like you to tell me the author and for bonus marks from which novel it was taken.

‘Ever seen a leaf - a leaf from a tree?’
‘I saw one recently - a yellow one, a little green, wilted at
the edges. Blown by the wind. When I was a little boy, I used to
shut my eyes in winter and imagine a green lef, with veins on it, and
the sun shining …’
‘What’s this, an allegory?’
‘No; why? Not an allegory - a leaf, just a leaf. A leaf is
good. Everything’s good.’
‘Everything. Man’s unhappy because he doesn’t know he’s happy
… he who finds out will become happy at once, instantly …’
‘And what about the man who dies of hunger, and the man who
insults and rapes a little girl. Is that good too?’
‘Yes, it is. And the man who blows his brains out for the
child, that’s good too. Everything’s good …’
‘When did you find out you were so happy?’
‘I was walking about the room. I stopped the clock … It was
twenty-three minutes to three.’

Dostoevsky, The Possessed