The first principle is known as The Rule of Sarahs.
This one is remarkably simple, and the logic behind it was formulated at least in part by boomzilla and delwyn. It is based on the fundemental law that "all Sarahs are dodgey". Think about those simple four words for a moment. Now, think of as many Sarahs as you can. Our observations tell us that even if you cannot see the dodginess on the surface, it will be there... somewhere...
The second principle is The Rebecca Conundrum.
Just as all Sarahs are dodgey, all Rebeccas share one unifying, though unusual quality. However, unlike Sarahs (the basic dodginess of which can be observed at any time regardless of environment), the Rebecca Conundrum can only be observed when two Rebeccas come into contact with eachother. Rebeccas, upon first meeting eachother, will imediately for either a close bond which will unite them in friendship until their dying days OR will instantly hate eachother to the point of calling out a blood feud. No-one knows exactly why or how this happens, only that Rebeccas will either love or dispise eachother. Therefore, great care must be taken when attempting to introduce Rebeccas.
These two concepts are but the beginning of a unifying understanding of the more deadly of the species. You are been warned. This has been a public service announcement.