Try this exercise, if you close your eyes for example, and imagine that you are lying in a beautiful beach, just imagine that you are on the beach now and you close your eyes, you can smell the sea breeze, and you hear the sound of waves on the beach, and feel the warmth of the sun, you may even hear To the cries of seagulls from afar, all these things have happened inside your mind. Now, do not know your mind whether this is just a fantasy of you, or that it exists in fact, you are the only one who can actually determine it, it is true or not.