Imperturbability refers to the state of being calm and composed, especially in the face of adversity or disturbances. It is the ability to remain unruffled and unaffected by external and internal factors.
Returning to the concept of interdependent arising, disturbances are an integral part of external reality. Everything is impermanent and subject to change. True stability and security come from accepting change, and no security should rely on stability of external phenomena. The ultimate security lies in the wisdom and knowledge of the impermanence of external phenomena. The specific interaction with any given phenomena is relative and does not contribute to ultimate security.
The lowest level of interaction with external phenomena occurs when ill-will, covetousness, and presumption arise. "Ill-will" refers to having negative or malicious intentions towards someone. "Covetousness" refers to an intense desire to possess something that belongs to someone else. "Presumption" refers to making assumptions or taking actions without proper justification or authority. It is not that external phenomena inherently induce these feelings, but rather that the underdeveloped mind gives rise to such emotions. It is not possible to achieve ultimate security without conquering this lower base. By practicing abundance and exultance, which means having an unlimited quantity or supply of everything and feeling joyful or triumphant as a result, one can develop the mind in a way that prevents covetousness, ill-will, and presumption from arising. Instead, the mind remains calm and tranquil when faced with such phenomena.
Another factor that contributes to disturbance of the mind is the dispossession of material/immaterial form that used to give sustained feeling of pleasantness through the ownership of it. Material or immaterial forms are composed of smaller elements, and they are designed in a way that can evoke either pleasant or unpleasant feelings. By practicing meditation and deconstructing material possessions into their smaller elements, one can gain the understanding that the foundational elements are devoid of any inherent pleasantness or unpleasantness.
The main cause of disturbances in the two processes mentioned above is the inability to accept impermanence. By practicing and meditating on impermanence, the mind will develop in a way that it is not disturbed by the impermanence of sensory, material, and immaterial existence. Eventually, there will be a stage where the interaction between the mind and external phenomena is not disrupted by the things that used to hinder it in the past. The brain's default mode will change, and neural pathways will be restructured. It will be like experiencing taste through your eyes or seeing through your tongue.
Mastery is achieved over the interaction of external phenomena and the mind, in both the present and, hopefully, the future. This necessitates sustained practice of knowledge and wisdom. However, the past interactions of the self with the external world, including relationships, memories, fears, and other aspects of existence, also exert a significant influence. They give rise to thoughts and feelings that are distinct from those arising solely from present interactions with external phenomena.
Practicing non-duality and meditating on it can lead to an understanding that the self is not separate from the body, mind, feelings, consciousness, being, non-body, non-mind, non-feelings, non-consciousness, and non-being. The illusion of self gradually diminishes by practicing unity with the void, the forest, and the external world. Previously, when the self identified with or was identified by something else, all such delusions dissolve through practice. Eventually, the mind becomes empty of self and its connection to stored information.
So far, wisdom has been described as consisting of two elements: the infinite nature of space/forms and the void nature of the mind. It is a state of complete freedom where the interaction with external or internal phenomena is pure, without any corrupting influences, and is eternal. The eternal nature is a result of the absence of corrupting influences in the mind. This is a state of pure calm and bliss, free from volatility and disturbances. By practicing in this way, one can cultivate the ability to remain undisturbed and unaffected.