Just a thougth that occured. Looking at history I am under the impression that at the large scale mankind progresses towards liberty though there are times where liberty diminished or vanishes completely. A good example would be ancient Athen as quite free city, the dark age as an age of opression and the renaissance as the literal revival of ancient ideals such as liberty.
Given this, quite low quality, empirical evidence, does anybody think that liberty is inevitable? Maybe in the sence marx thinks, communism is inevitable.