Last week I went to the movies and watched Inception, a movie about the boundaries of reality explored in the lucid dreams of the main characters.
The main question posed in this flick is how we can know whether we are dreaming. This is an age old question in philosophy and was most famously explored by French soldier-philosopher René Descartes. In his magnificent philosophical book Meditations on First Philosophy, Descartes doubts all sources of knowledge and asks himself:
How often, asleep at night, am I convinced of such familiar events — that I am here in my dressing gown, sitting by the fire — when in fact I am lying undressed in bed. … As I think about this more carefully, I see plainly that there are never any sure signs by means of which being awake can be distinguished from being asleep.
Descartes doubt in his first meditation is total. Descartes is, however, not actually convinced that we can not know anything. He merely engages in a thought experiment to find the one true source of knowledge. Eventually he concludes famously that the only thing he can know is that he is a thinking being — I think therefore I am.
The storyline in Inception refers back to Descartes’ argument. In the movie the main characters experience a collective dream and even dream within a dream, within a dream, within a dream. The main characters know that it can be confusing to distinguish our waking reality from our dreaming one and they use a little trick to determine where they are.
Although Descartes thinks he can not know whether he is dreaming or not, there are clear differences between our waking and dreaming reality.
Most importantly, the waking reality is bounded by causality. If you hit somebody in the face in reality, there will be consequences. If you do the same in a dream, there are no consequences. The other difference is that waking reality is a shared experience. You can hit your best friend in the face in a dream, but she will not show up with a bruise in waking reality. Even if there was no mark, your friend will not have experienced being hit by you in her dream. Dreaming reality is a private experience.
The question remains, however, which reality we should give primacy, the waking world or the dreaming one. The empiricist philosopher might argue that since our experiences in waking reality are shared and can be confirmed by others. This seems an attractive line of reasoning, but the question of reality can not be resolved by democratic means. Just because we all agree on something does not mean that it is the truth.