Like other novels by George Eliot, The Mill on the Floss articulates the tension between circumstances and the spiritual energies of individual characters struggling against those circumstances. A certain determinism is at play throughout the novel, from Mr Tulliver's grossly imprudent inability to keep himself from "going to law", and thereby losing his patrimony and bankrupting his family, to the series of events which sets Maggie and Stephen down the river and past the point of no return. People such as Mr Tulliver are presented as unable to determine their own course rationally, and forces, be it the drift of the river or the force of a flood, are presented as determining the courses of people for them. On the other hand, Maggie's ultimate choice not to marry Stephen, and to suffer both the privation of his love and the ignominy of their botched elopement demonstrates a final triumph of free will.
Critics assert that Maggie's need for love and acceptance is her underlying motivation throughout The Mill on the Floss, and the conflicts that arise in the novel often stem from her frustrated attempts at gaining this acceptance. Alan Bellringer has commented, "The two main themes of the novel, growing up and falling in love, lend themselves to amusement, but it is stunted growth and frustrated love that are emphasized." Commentators have often focused on the constant rejection of Maggie's talents and mannerisms by her family and society. Even the cultural norms of her community deny her intellectual and spiritual growth, according to Elizabeth Ermarth, "They are norms according to which she is an inferior, dependent creature who will never go far in anything, and which consequently are a denial of her full humanity."