Time pervades all human experience, but what exactly it is isn't so easy to explain. On one side was henri bergson, a fantastically famous philosopher whose ideas about time had already influenced a generation of thinkers and writers. On the other albert einstein, 20 years younger, thanks to his mind bending theory of relativity, which said that time was, well, relative. Their debate set the tone for scientific and anti-scientific debates even a century later.