All of the above refers to Dhamma as a collection of specific medicines for use with specific illnesses, the diseases of the defilements. Now there is another kind of disease which is even more extensive. Just now I spoke of the troubled and disturbed mind. Now this very mind, as well as the body, which together we call a "life," being compounded of the five khandhas1, are all saṅkhāra, conditioned things. All saṅkhāra have certain characteristics. They are unstable, unenduring or suffering, and not self, they do not come under anybody's power other than the natural process of cause and effect2. All saṅkhāra conform to these Three Characteristics, known in Pali as the tilakkhana. That all conditions are unstable, suffering and not self is another kind of disease, one that is inherent in all saṅkhāra, khandhas, body and mind. It is the disease of their imperfection, of their deprivation. Being imperfect they are naturally hounded by conflict, struggle and change.
This imperfection also causes problems in the mind, so people suffer not only as a result of the workings of the grosser defilements, which we can clearly see arising from time to time in the mind, but also from the more subtle defilement of not knowing the true nature of life3. Suffering arises because of the very imperfection of conditions, of their being subject to the Three Characteristics. This is a more profound kind of disease, one which we must cure in order to really transcend suffering. It is not enough to simply try to cure the greed, hatred and delusion that are constantly arising in the mind, we must also clearly know the nature of life, that it is bounded by these Three Characteristics.
If we don't understand this, we will cling to the five khandhas as being a self or belonging to self, demanding of them not to change, but no matter how much we cling to them they won't conform to our wishes, they simply follow causal conditions. Clinging to them only causes disappointment and suffering.
Thus, on the deeper level, we could say that beneath the greed, hatred and delusion, the real cause of suffering is the imperfect nature of conditions, ignorance of which causes the defilements of greed, hatred and delusion to arise in the mind.
We must therefore study the diseases of our lives on two levels. The disease which is most apparent is the disease of the various defilements: greed, aversion, delusion, conceit, stubbornness, jealousy, stinginess and so on, which we see all around us. However, looking more deeply, we find that all disease is caused by the nature of conditions, which are bound by impermanence, stressfulness and insubstantiality (anicca, dukkha and anatta).