Things exist because they can't

If they could, then they'd have to come from something, which would come from something else, and eventually terminate somewhere. Where did that somewhere come from? It can't come from anywhere because, when you trace back each thing to its origins, it is the root. Therefore, it can't exist, and hence things that come from it can't exist, therefore they exist because they can't!

A more rational way of putting this is: The concepts existence and non-existence each cannot be defined without the other. Therefore, existence is only possible because of non-existence, and vice-versa. This is all very Tao.