The theme of The Mayor of Casterbridge appears to be the arbitrary and almost always malign workings of the universe and blind chance upon the destinies of men. Such evil, unrelenting machinations bring pain and suffering upon the characters in the novel, and there is no escape except in a day-to-day acceptance of life.
Much has been written concerning Hardy's famous pessimism. However, in The Mayor of Casterbridge, despite the workings of blind fare, the occurrences of chance, and the vagaries of a hostile natural environment, Michael Henchard is still responsible for his own fate. If he had not sold his wife in a fit of drunken self-pity, the painful events would not have ensued. If he had not overspeculated in order to ruin Farfrae, it would not have mattered if it rained, or snowed, or hailed. Certainly in his many years as corn-factor and leading businessman he had come through other natural disasters. It is only in this one case that he lets his keen sense of rivalry and lust for revenge cause him to speculate recklessly.
Nor is Hardy indifferent to man's senseless cruelty to his brother. He structures the events so that even Elizabeth-Jane has become too prim and unrelenting in her firm stand on Lucetta and Henchard. He is unsparing in his portrayal of the lower-class townspeople for their cruel and vicious "skimmity-ride."
And, in Henchard's case, since he is the focal point of the novel, Hardy is saying that wickedness and evil will return to the perpetrator in full cycle, in like measure. He is indeed saying that the evil which man does will not only live after him, but it — evil, not fate — will dog man's steps until poetic justice has been satisfied.
One last word. Let the reader observe Henchard's behavior after Elizabeth-Jane has come to dwell with him, and the motivations for that behavior. Though Henchard's actions are somewhat tempered with the base emotion of jealousy — which is only human — all that he does is motivated by love of Elizabeth-Jane. He lies to Newson because he doesn't want to lose Elizabeth-Jane; he leaves Casterbridge because he cannot bear Elizabeth-Jane's scorn; he returns to show his love and to be forgiven; he departs forever so as not to cause his foster-daughter pain and embarrassment; and finally, he writes a will whose requirements will blot out his existence from the eyes of men, especially from Elizabeth-Jane whom he does not wish to hurt. There is nobility in Henchard because he willingly takes upon himself suffering as an expiation for the sins of his life. He carries his suffering and his love for Elizabeth-Jane in silence. And when man can rise to stature and nobility as Henchard does at the end of The Mayor of Casterbridge, then the dominant chord Hardy has struck swells to a bold theme of hope for humanity.