The Categorical Imperative

I've had a few ideas for different blog posts, but I've found that many of them lead back to what is called the Categorical Imperative. So I've decided to just explain this concept, and hopefully it will aid those who frequent this blog (Pat and Dax) in better understanding crap that I may post in the future.
First of all, the Categorical Imperative is one of Kant's theories (it is, in fact, the fulcrum of the moral branch of his philosophy). The principle is this: Always act according to that maxim whose universality as a law you can at the same time will. Now I know that this is one of those really long sentences that you don't feel like tackling right now, but before you go back to tetris, let me try and explain it more clearly. What it is saying is, that you should only do something if you think it would be good if everyone were to do the same thing. An example of something that would not work under the Categorical Imperative: you want to borrow money from a friend, you tell them you'll pay them back at the first opportunity, however you know that you have no intention of paying them back at all. If we put this into the formula we see it cannot work; if everyone were to ask for money without intending to pay back their debtors, not only would no one get paid back, but no one would lend money because everyone would know that everyone was lying. Lying is something that only works when the majority of humanity doesn't lie about the majority of things.
Now for the sake of not making this an overly lengthy post I'm going to end things here. It should be known that this isn't quite the full concept of the c-i, but it is a crucial idea to grasp. If you want to know more about it here's a link to follow, I'll probably be posting more about this sort of stuff in the future.