“I am by turns a petulant adolescent and a mature man, a melancholy loner and a wit telling actors their trade. I cannot decide whether I'm a philosopher or a moping teenager, a poet or a murderer, a procrastinator or a man of action. I might be truly mad or sane pretending to be mad or even mad pretending to be sane.”

“Pretend to be mad and talk a lot. Then — and this is the important bit — do nothing at all until you absolutely have to and then make sure everyone dies.”

“Don't ever call me mad, Mycroft. I'm not mad. I'm just ... well, differently moraled, that's all.”

“You'll like it here; everyone is quite mad.”

“Sometimes I don't know whether I'm thening or nowing.”

“By spiritually I merely mean that I feel I have good in my soul and am inclined to follow the correct course of action given a prescribed set of circumstances.”

“Scientific thought - indeed, any mode of thought, whether it be religious or philosophical or anything else - is just like the fashions that we wear - only much longer lived. It's a little like a boy band.”