“Sheldon: Why’d you set it for the day before yesterday?
Leonard: Because I want to go back and keep myself from getting a time machine.
Sheldon: You can’t. If you were to prevent yourself from buying it in the past, you would not have it available in the present – travel back and stop yourself from buying it, ergo you would still have it. This is a classic rookie time travel mistake.
Leonard: Can I go back and prevent you from explaining that to me?
Sheldon: Same paradox, if you were to travel back in time and, say, knock me unconscious, you would not then have the conversation that irritated you, motivating you to go back and knock me unconscious.
Leonard: What if I knocked you unconscious right now?”

 The Big Bang Theory

I personally think that this way of acting is sensless, as science, technology, and human knowledge exist as a whole to serve human beings. We will always have to grab more than one “category” on which general knowledge is nowadays subdivided to reach this purpose. It is pure fiction to think that you have a “medical problem”, or a “legal problem”, there is usually much more behind. Labels exist just because we humans can’t achieve a complete vision of all knowledge, we are not that smart, so each one of us must work on a part of it, to contribute then to mankind with his achievments, discoveries, and, which is more important, mistakes.”

Santiago de Compostela, 02-01-09

“Save the cheerleader, save the world”- Hiro Nakamura