"No man was more filled with the sense of this bellicose basis of all cheerfulness than Dickens. He knew very well the essential truth, that the true optimist can only continue an optimist so long as he is discontented. For the full value of this life can only be got by fighting; the violent take it by storm. And if we have accepted everything, we have missed something — war. This life of ours is a very enjoyable fight, but a very miserable truce. And it appears strange to me that so few critics of Dickens or of other romantic writers have noticed this philosophical meaning in the undiluted villain. The villain is not in the story to be a character; he is there to be a danger — a ceaseless, ruthless, and uncompromising menace, like that of wild beasts or the sea. For the full satisfaction of the sense of combat, which everywhere and always involves a sense of equality, it is necessary to make the evil thing a man; but it is not always necessary, it is not even always artistic, to make him a mixed and probable man. In any tale, the tone of which is at all symbolic, he may quite legitimately be made an aboriginal and infernal energy. He must be a man only in the sense that he must have a wit and will to be matched with the wit and will of the man chiefly fighting. The evil may be inhuman, but it must not be impersonal, which is almost exactly the position occupied by Satan in the theological scheme."
~G.K. Chesterton: Charles Dickens, Chap 11.