Artemis Fowl: Time Paradox

I am now currently reading Artemis Fowl.  This one is about a 14 year old genius who's mother is dying of a magical disease known as Spelltropy.  There is no longer a cure since the cure is made from the brain fluid of a now extinct Lemur.  To add insult to injury, it turns out that Artemis sold the lemur to a group known as the Extinctionists, an organization that enjoys killing off species to ensure human control of the Earth (doesn't make any sense to me either.)  However, Artemis has a plan to go back in time, believing that if one goes back in time, then, in theory, you have already gone back in time so the past can not be changed.  Does anyone else believe in this time traveling theory?