Tell, me, is this train inside or outside your mind?
Outside, of course.
Picture a grey, round rock, a boulder larger than your self.
Tell me, does this rock exist inside or outside your mind?
Inside, of course.
Are you sure? There are many rocks just like it in this world.
But this one exists only in my mind.
Tell me, how much does this rock weigh?
I have no idea. A lot.
Then why are you carrying it around with you? If you carry this boulder around, you will only hurt your back. You can put it down. You can let it simply dissolve.
Thank you, master.