Observe duḥkha

Does the first noble truth mean "there is suffering: and we need the path to eradicate it?” Or “does suffering have a dual nature (such as without suffering there is no joy)” ?

The "suffering" in Buddhism can actually be viewed from three aspects. It is not necessarily negative and pessimistic. 

For a long time, the translation of "dukkha" into "suffering" is limited and very easy to cause misunderstanding. 

In fact, when the Buddha told us "dukkha", he just conveyed the FACT, the TRUTH, and that is just a Natural Situation in the phenomenal world.

The three kinds of 'dukkha' are:

1. duḥkha-duḥkha

This is what we called Ordinary duḥkha, Concrete duḥkha or Physical duḥkha; it is a direct suffering that one experiences in sickness, exhaustion, hunger, torture, etc., apparently related to all sorts of unpleasant experiences. 

2. vipariṇāma-duḥkhatā

We called it duḥkha of decay, the duḥkha that people experience when they lose things that they are attached to / delighted to, e.g. the loss of the state of joy, happy holidays are coming to an end etc., evidently related to all sorts of pleasant experiences. 

3. saṃskāra-duḥkha 

We called it the duḥkha caused by change or the duḥkha produced by impermanence, e.g. whether we want to accept it or not, and no matter pleasant or unpleasant experience, TIME is constantly passing by every second, we are constantly in the process of CHANGE without the slightest pause.

The above three duḥkhas are all normal things in life, aren't they? That's why I said that “when the Buddha spoke of duḥkha, is just presented the Facts and the Truth to us.”

Now, is “ERADICATE” a suitable word here? 

My opinion is, we should ERADICATE the unwholesome roots, such as greed, hatred, jealousy, arrogance etc., because they are the fundamental cause of our suffering.

For duḥkha (no matter which duḥkha), what we need to do is OBSERVE (the fact, the truth, the nature of the phenomenon) and learn to ACCEPT it.

The nature of reality and REALITY

The reality’s nature is some sort of nature that we can observe and perceive easily, compare to the Reality’s nature.

Through impermanence, we recognize the reality from the phenomenon of arising and ceasing. Again, from these phenomenon, we also realize that nothing can be controlled by us. What we can do is just try our best to maintain, to take care, to protect etc., by adding on certain conditions. 

For instance, we try to eat healthy, get good sleep, keep routine physical workouts etc., to maintain our physical health. However, the reality is, we can only try our best to preserve but we can’t really determine nor dictate the consequences.

Deep inside the phenomenon of changing lies a nature which we can’t really discern easily, which is the Reality’s nature —— emptiness (sanskrit : śūnyatā, śūnya). The Emptiness here is not a nihilistic concept, It definitely doesn’t mean empty, nonexistence or nothing at all etc. The nature of Emptiness, indeed, make room for all things to change momentarily.

Without the Reality —— Emptiness, how can something arise? And, without Emptiness, how can something cease? Without Emptiness, those already existed (or so-called existence), will never cease. Without Emptiness, those that have yet to appear, will never arise.

All the phenomenon of impermanence, the reality’s nature is based on the Emptiness, which is the Reality’s nature.