What is a Dream Argument?
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 whether it is in fact reality.
While people dream, they usually do not realize they are dreaming (if they do, it is called a lucid dream). This has led philosophers to wonder whether one could actually be dreaming constantly, instead of being in waking reality (or at least that one cannot be certain, at any given point in time, that one is not dreaming). In the West, this philosophical puzzle was referred to by Plato (Theaetetus 158b-d) and Aristotle (Metaphysics 1011a6). Having received serious attention in René Descartes‘ Meditations on First Philosophy, the dream argument has become one of the most prominent skeptical hypotheses.
In the East, this type of argument is well known as “Zhuangzi dreamed he was a butterfly” (莊周夢蝶 Zhuāngzhōu mèng dié): One night, Zhuangzi (369 BC) 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.
Some schools of thought in Buddhism (e.g., Dzogchen), consider perceived reality literally unreal. As a prominent contemporary teacher, Chögyal Namkhai Norbu, puts it: “In a real sense, all the visions that we see in our lifetime are like a big dream […]”. In this context, the term ‘visions’ denotes not only visual perceptions, but appearances perceived through all senses, including sounds, smells, tastes and tactile sensations, and operations on received mental objects.