The “dream argument” is the postulation that the act of dreaming provides preliminary evidence that the senses we trust to distinguish reality from illusion should not be fully trusted, and therefore any state that is dependent on our senses should at the very least be carefully examined and rigorously tested to determine if it is in fact “reality.”
While people dream, they usually do not realize they are dreaming. This has led philosophers to wonder whether one could actually be dreaming constantly, instead of being in waking reality, or at least that one can’t be 100% certain that he or she is not dreaming. In the West, the philosophical puzzle is referred to in writings as early as Plato and Aristotle. Having received serious attention in René Descartes’ Meditations on First Philosophy, the dream argument has become one of the most popular skeptical hypotheses.
In the East, this type of argument is well known as “Zhuangzi dreamed he was a butterfly”. It relates that one night Zhuangzi dreamed that he was a carefree butterfly flying happily. After he woke up, he wondered how he could determine whether he was Zhuangzi who had just finished dreaming he was a butterfly, or a butterfly who had just started dreaming he was Zhuangzi. This was a metaphor for what he referred to as a “great dream.”
He who dreams of drinking wine may weep when morning comes; he who dreams of weeping may in the morning go off to hunt. While he is dreaming he does not know it is a dream, and in his dream he may even try to interpret a dream. Only after he wakes does he know it was a dream. And someday there will be a great awakening when we know that this is all a great dream. Yet the stupid believe they are awake, busily and brightly assuming they understand things, calling this man ruler, that one herdsman ‑ how dense! Confucius and you are both dreaming! And when I say you are dreaming, I am dreaming, too. Words like these will be labeled the Supreme Swindle. Yet, after ten thousand generations, a great sage may appear who will know their meaning, and it will still be as though he appeared with astonishing speed.