We accept dream-images as reality because in sleep we have no other impressions to compare them with, being detached from the external world. However, the reason why we believe in the truth of our hallucinations is not that we have no opportunity, in sleep, to put them to the test. Dream is capable of feigning all such tests for our benefit – of showing us, for example, that we are touching the rose we can see, yet at the same time dreaming.
