The alchemists of past centuries tried hard to make the elixir of life: ... Those efforts were in vain; it is not in our power to obtain the experiences and the views of the future by prolonging our lives forward in this direction. However, it is well possible in a certain sense to prolong our lives backwards by acquiring the experiences of those who existed before us and by learning to know their views as well as if we were their contemporaries. The means for doing this is also an elixir of life.