I am having difficulty understanding the idea of interdependent origination within the following text. It is from The Essence of Buddhism by Traleg Kyabgon. I am finding this book very useful as a refresher on the basic philosophy of Buddhism, especially because it includes Tibetan Buddhism. However this section, which talks about one of the two main ideas in Buddhism, seems to rely on terminology that gives me the impression of circular reasoning.
"How, then, do things come into being? They come into being because of what is called interdependent origination, or pratitya-samutpada—that is, due to causes and conditions. This implies that things do not have inherent existence, because if they had any kind of essence or independent existence there would be no need for the whole idea of causality. Nagarjuna says: “The origination of inherent existence from causes and conditions is illogical, since if inherent existence originated from causes and conditions, all things would thereby become contingent. How could there be contingent inherent existence? For inherent existence is not contingent; nor is it dependent on another being. So the very idea of causality involves the notion that things are contingent. There is no being that can exist on its own without depending on anything else; no self-sufficient being. Everything is interdependent. Everything that exists on both the physical and mental plane involves the idea of interdependence, or pratitya-samutpada.”
I would very much appreciate an explanation, in clear English and without reliance on terminology (because it appears to be explaining by self referencing concepts and terms) of this basic idea. My guess is that the author is assuming that I already know something which I do not. References to online sources would be appreciated, if you can explain it yourself that would be terrific, and most of all if you can refer me to a clear, translation of the Buddha's original words about this that would be splendid.