The book from which this excerpt is taken, Emptiness and Omnipresence: An Essential Introduction to Tiantai Buddhism
http://www.amazon.com/Emptiness-Omnipresence-Essential-Introduction-Philosophies/dp/025302112X?ie=UTF8&qid=1463112243&ref_=tmm_pap_swatch_0&sr=1-1, traces the development of Buddhist through from the Four Noble Truths to Emptiness to the Buddha-Nature to the Lotus Sutra, and finally to the doctrine of omnipresent interfusion of all realities in Tiantai (Tendai) Buddhism. It all begins with the "paradox of suffering":
Buddhism begins and ends with the problem of suffering. More specifically, Buddhism begins with the Four Noble Truths. The treatment of suffering there seems at first glance disappointingly simple, almost simplistic. The First Noble Truth tells us that all experiences necessarily involve suffering. The Second tells us why this is: this suffering is caused by desire, or craving, and attachment to desire. The Third asserts that the end of this cause (desire), and hence of this effect (suffering), is attainable. The Fourth tells us how.
Often this formula is understood in a very straightforward way: we suffer when things don't go the way we want them to. Suffering happens when we desire what is not the case. Usually when this happens, we try to make "what is the case" conform to our desire: we try to get what we want. The Buddha, on this interpretation, makes the surprise move of approaching the dissonance between desire and reality from the opposite side: instead of changing the reality, change your desire.
But this way of understanding the problem may strike many as wildly unsatisfactory. For one thing, can we really change what we desire? The traditional answer is yes, for the Fourth Noble Truth outlines how this can be done: by following the Eighfold Path of discipline, meditation and insight. It is a question, ultimately, of enlightened self-interest. For this process involves coming to see clearly that all experience involves suffering, and thus that our desire for certain experiences was based on a false belief--namely, that these desired experiences would actually save us from suffering. Our desire for something other than what is the case was based on a misconception. We come to see, in this process, that it is unreasonable, and not in our own interest, to desire what is not the case.
Note however that this still means promoting our most basic desire: to avoid suffering. All our endeavors were aimed at maximizing pleasure and minimizing suffering, in more or less complex or indirect ways. It's just that we were doing it in an unskillful, self-defeating way. But for any of our experiences to be any good--even the experience of the end of suffering--this desire to avoid suffering at least must remain in place. If we really "eliminated" desire, there would be no desire there to receive, appreciate, enjoy the end of suffering when we attained it. But in that case, the end of suffering would be in no way preferable to suffering--for what makes either one worth anything is simply that it gives us something we want.
This brings up a more searching problem in this understanding of the Four Noble Truths: isn't this "ending of desire" in order to end the suffering it entails kind of like cutting off your nose to spite your face? Or, more forcefully, a bit like cutting off your head to cure a headache? Just to pile on the clichés, it seems to be a case of throwing out the baby with the bathwater. As Nietzsche said, we do not much admire a dentist who cures toothaches only by extracting the tooth entirely--this seems a crude, somewhat fanatical, almost violent way to solve a problem that requires a more nuanced solution. Do we really want to want nothing, to take no joy in things, to passively accept whatever happens and have no opinion about it at all, no will, no initiative, no desire?
Of course, this is a crude caricature of the Buddhist position. But it is one that sometimes lurks in the background even of relatively sophisticated presentations of Buddhist thought and practice. Even a perfunctory experience of Buddhist practice, however, reveals that something is wrong with it--for the end of desire turns out to be a profoundly joyful experience, in a way that is not easy to describe or analyze within the terms of experiences of joy premised on desire in the more ordinary sense. One finds, to one's surprise, that this acceptance of things exactly as they are produces an intense happiness, as intense as if one had attained something one had been fervently desiring without realizing it. It causes one to re-evaluate what one meant by desire, what one meant by pleasure, even what one meant by experience.
To try and get at why this is so, we must note that the Four Noble Truths actually present a profound paradox. Look at the logic:
It is by ending desire that suffering is ended.
But desire, by definition, is the attempt to get away from some suffering. Desire is the desire to end suffering.
Therefore: it is by ending the desire to end suffering that suffering can be ended!
Let's put that another way: suffering can only be ended by no longer trying to end suffering!
It is the acceptance of suffering, the recognition of suffering, the full realization of suffering, that ends suffering. What can this mean? How is this done? That is the adventure that the subsequent two and a half millenia of Buddhist thought open up for us.