But sometimes you can't figure everything out because you can't ever really understand other people. You can't understand why they do what they do. You just have to accept a little mystery, Ben. People are mysterious, the world is mysterious. You can't know everything. You're not supposed to. This isn't a history book. It's just the world. It's a messy place.
An emotion is a thought, yes, an idea, but it is also a sensation, an ache in your body. Desire, love, hate, fear, repulsion - you feel these things in your muscle and bones, not just in your mind.
Genes are not simple triggers. No one is hardwired to commit murder or any other crime. Our actions are always the result of stupendously complex gene-environment interactions, and environment is likely to remain the more important influence by far.