No, Sherlock doesn't need another brain. But he could benefit from an extra heart.
Sherlock: If the occasional pile of clutter offends you, by all means move it. John: Last time I tried that I was bitten by a large spider you appeared to be using as a bookmark.
Sherlock: You're keeping a SCRAPBOOK. Only old ladies and pre-pubescent girls keep scrapbooks, John. John: It's not a scrapbook, Sherlock. I'm collecting papers relevant to the cases. It helps me remember the details. And it was locked away in my des...
then he jumped.. I owe him so much. I needed him. I still do. But he's gone. He told me once that I shouldn't make people into heroes. He said that heroes didn't exist and that even if they did he wouldn't be one of them. which goes to show. he wasn'...
John [to Sherlock]: You're incredible. A genius. A good friend. And a lousy driver.