Dreaming and Waking
It is not reasonable to think that a dreamer actually goes out in order to experience the objects seen in the dream, because of the discrepancy of the time involved in such a journey. Nor does he, when awakened, find himself in the places seen in the dream.
The dreamer, after awaking, realizes the illusoriness of the conversations he had with friends etc. in the dream state. Further, he does not possess in the waking state anything he acquired while dreaming.
The dream body is unsubstantial because the other i.e. the physical body, different from it, is perceived. Like the dream body, all things cognized by the mind are unsubstantial.
Since the experience of objects in dreams is similar to the experience of objects in the waking state, waking experience is regarded as the cause of dream experience. It is only by him who admits waking experience to be the cause of dream experience that waking experience can be regarded as real.
All entities are said to be unborn, since birth cannot be established as a fact. It is utterly impossible for the unreal to be born of the real.
...And how utterly impossible it is for the real to be the cause of the unreal!