Knowing if you’re awake seems simple. Why has it vexed philosophers for centuries?
Knowing what separates wakeful reality from dream states seems rather simple on its surface. After all, even if a dream feels quite real in the moment, it’s unbound from continuity and the natural laws of our (presumed) waking lives. Yet proving that you’re awake, rather than just intuiting it, has been a perilous task for philosophers across the centuries. Beginning with the ancient Chinese philosopher Zhuang Zhou’s famed butterfly dream, this TED-Ed animation tackles how thinkers from Al-Ghazali in medieval Persia, to René Descartes and Thomas Hobbes in 17th-century France and England, to neuroscientists today have approached the question of whether we can ever truly know we’re awake.

videoKnowledge
A Kichwa activist on ayahuasca’s rise – and what it really means to her people
15 minutes

videoNature and landscape
Scenes from Aboriginal Australian pottery chart the turn of the seasons
7 minutes

videoEthics
What’s an idea worth? How prominent thinkers have understood intellectual property
6 minutes

videoMathematics
Spiral into the ‘golden ratio’ – and separate the myths from the maths
4 minutes

videoKnowledge
Why David Deutsch believes good explanations are the antidote to bad philosophy
10 minutes

videoChildhood and adolescence
‘Do worms cry?’ – and other questions collected from the mind of a curious child
4 minutes