What iis the nature of mind? Why do we need to know? We need to know because it is where we 'live'. It is our consciousness, 24/7. It is all our thoughts and feelings, the source of all pleasure and pain. It is where suffering and joy take place.
We associate ourselves with our mind. In our daily lives, 'we ARE the sum total of our thoughts and feelings'. When events transpire to bring us suffering, WE suffer. The same with happy events. We associate ourselves so completely with our minds that we overlook the possibility that we are WRONG.
Buddhist philosphy clearly states, "we are NOT our minds". That belief is a dangerous and punishing illusion.
Is it possible that the Buddhists are actually correct? If so, what is the evidence? It may be as simple as observing our thoughts/feelings over a period of time. They change from moment to moment. Even the thoughts/feelings that occur after some horrific shock are not constant.
We may recall that the intensity of horrible feelings ebbed and flowed. If we thought about the situation we might even have developed physical symptoms that coincided with thoughts/feelings of dread.
During any particular period of suffering, we might have even felt "OK" for periods of time. And this despite the fact that nothing changed about the outside circumstances.
Our fluctuating mind-sets, our feelings about events are what constitutes our minds. They are not constant or continuous. We can even alter the way we perceive life's events, re-frame to be less painful.