We need to know what a limit is. It is the value that some variable approaches but never reaches if one of their parameters approaches a certain point. Example : When X approaches but never quite reaches 0, X^2 approaches but never quite reaches 0. It's the limit of x going to 0 for X^2 . The Limit. A limit implies the constant movement of some variable towards a certain point. So we NEED to talk about X, or a variable of any kind, if we want to calculate a limit. He just said the number 2, a constant number, not a variable, we can't work with it.