The Shurangama Sutra tells the truth in one sentence: "What you see is the heart rather than the eyes, what you hear is the heart rather than the ears, what you hear is the heart rather than the nose, and what you taste is the heart rather than the mouth". Just like sweeping the floor in life, people can sweep the floor, not a broom. The broom is just a working shell in our hands. By the same token, our eyes, ears, nose, tongue, body and mind are only six tools of the heart, so with the help of eyes, ears, tongue, body and mind, our heart can see the color, sound, smell and touch of these six dusts. So it is the "heart" that can really be seen and touched, not six.