"It is quite true what philosophy says; that life must be understood backwards. But then one forgets the other principle: that it must be lived forwards. Which principle, the more one thinks it through, ends exactly with the thought that temporal life can never properly be understood precisely because I can at no instant find complete rest in which to adopt a position: backwards."
Soren Kierkegaard, Journals IV A 164 (1843)
Philosophers have hitherto only interpreted the world in various ways; the point is to change it.
Marx, Theses On Feuerbach (1845)