Since man first became aware of time with the passing of the seasons the nature of time has been challenging philosophers and scientists alike. Starting with the "flux doctrine" of "Heraclitus" according to which everything is constantly altering ("You cannot step twice in the same river") to Henry Bergson who was one of the first philosophers to incorporate cinema into a philosophical discourse philosophers have wrestled with the concepts of time and memory. In literature Marcel Proust of course comes to mind with his huge novel "Remembrance of Things Past" and on the scientific side Albert Einstein with his "Theory of General Relativity." Einstein posited that time is simply another dimension which with space forms a four-dimensional space-time continuum (that was until recently when seven more dimensions were added with the M-theory the "theory of everything").