True reality is what appearance is not. So one way of knowing the true reality is to know that everything you see and experience, everything you think about, is not true. Just eliminate one thing after another: not this, not that. Everything goes. It all goes: everything you have experienced, everything you can experience, everything you can think, anything that can enter your mind. When all that goes, that, then, is the true reality. You cannot think of it, you cannot conceptualize it.