Suppose you press your eyeball with your finger, causing yourself to see a doubled image, such as a second moon beside the real moon. Now this second moon is only seen because of the pressure of the finger on your eye; there isn't really any second moon beside the real moon.
This does not mean, however, that if you don't want to be seeing a second moon, you should get rid of the false moon and see the real moon. If you simply remove the finger pressing your eyeball, there is no other moon beside the original moon. If you try to get rid of the second moon without removing the finger from your eye, you will never succeed. There are some people who think there is no real moon apart from this second moon, so they are in love with it. That is also a big mistake.
Those who do not put pressure on their eyeballs do not see a second moon to begin with; how could there be any debate about whether or not to get rid of the second moon? So the issue of the sameness or difference of the true and false mind arises because of pressing the eye of the fundamental with the finger of confusion.
-Zen Master Muso, Dream Conversations