"The mill" is first mentioned in Book the First, Chapter Five, which gives us our first introduction to the poverty of French society and how life there for peasants was so terrible at this time. Note how the mill is described and presented to us:
Samples of a people that had undergone a terrible grinding and re-grinding in the mill, and certainly not in the fabulous mill which ground old people young, shivered at every corner, passed in and out at every doorway, looked from every window, fluttered in every vestige of a garment that the wind shook. The mill which had worked them down, was the mill that grinds young people old; the children had ancient faces and grave voices; and upon them, and upon the grown faces, and ploughed into every furrow of age and coming up afresh, was the sign, Hunger.
Notice the dictino of this passage, and the way that the grinding process of the mill is described as "terrible" and it "grinds young people old." The description of children with "ancient faces and grave voices" reveal the way that "Hunger" is such an evident result of the poverty, which is of course what the mill symbolises. We can therefore see from this description that the mill and its function symbolises the way in which lives are destroyed and slowly eaten away by poverty, which of course gives us a valuable insight into the background of the French Revolution and the very real inequality that existed in France at that time.