How do you reason with a 3 year old?

This is a conversation Ben and I had this morning after he dropped his bowl of cheerios on the floor (luckily there was no milk in the bowl).

Me: "Ben, you need to pick those up."

Ben: "I don't want to."

Me: "Ben, please pick up the cheerios you dropped."

Ben: "No, I don't want to pick them up. It's not my fault. It's your fault."

Eventually, he picked them up. Ten minutes later he says to me, "mom, you're a really nice girl."

You can't help but love that little guy!