siddhartha mukherjee, welcome to hardtalk. thank you. a renowned oncologist, you're also now a feted writer. now, do you regard those two activities as entirely separate, or is the writing a way of you following your calling as a doctor? for me, i mean, like many other people, i write to think. you know, in order to figure out the questions that we, that you might find interesting, where are we in cancer? the only way for me to answer that question is to write, and sometimes, it might be writing a big book of facts, a 600 page book. sometimes the questions can be answered through a smaller article, sometimes they need to be scientific articles, but the writing is just a method for me to think. you've obviously thought about, worked on cancer for most of your professional life. at what point did you think to yourself, you know what, there might be a book in this that the general public would like to read? because cancer, let's face it, isn't necessarily a natural subject for a big selling book. well, the first time i put together a book p