The logic behind this rule is that there are often situations where it makes clear sense to allow one of something instead of none. However, if one decides to go further and allow N (for N > 1), then why not N+1? And if N+1, then why not N+2, and so on? Once above 1, there's no excuse not to allow any N; hence, infinity.
Many hackers recall in this connection Isaac Asimov's SF novel "The Gods Themselves" in which a character announces that the number 2 is impossible -- if you're going to believe in more than one universe, you might as well believe in an infinite number of them.
Hackers and computer scientists often like to call the first chapter of a publication `Chapter 0', especially if it is of an introductory nature (one of the classic instances was in the First Edition of {K&R}). In recent years this trait has also been observed among many pure mathematicians (who have an independent tradition of numbering from 0). Zero-based numbering tends to reduce fencepost errors, though it cannot eliminate them entirely.