What aspects of human nature does Anton Chekhov attempt to explore?
One of the aspects of human nature that Chekhov consistently explores is that of sincerity and genuineness. In many of his stories and plays, characters find themselves being torn by circumstances that demand that they be sincere with themselves in order to be sincere with others around them. This drive, propelled by circumstances, doesn't seem to work out well in the end, even when the characters do shed the pretense and become genuine and sincere. A example in point is the short story "The Lady with the Lapdog."
On holiday in Yalta, a man and a woman meet. Circumstances drive them together in passion--or assumed passion--then force them, in events afterward, to be sincere and genuine with themselves and each other. The end result is that he, Gurov, is dissatisfied with his quiet professional and family life and that she, Anna, is psychologically torn by her infidelity toward her husband and her new new feeling of repugnance toward him.
Chekhov seems to be suggesting in this thematic exploration of human nature that while we have a human need, a human drive, for genuine behavior and sincere feeling, we find self-destruction and unhappiness through it because, seemingly, society exists on one side of a thin veil and genuine, sincere expression tears that veil down bringing society's structure down with it.
Another example of the same exploration of this aspect of human nature is "A Dreary Story" in which Nikolay Stepanovitch gets what he desires by leading a sincere and genuine academic life only to find in the end that what he wants is what he now rejects.
I am afraid of suddenly dying; I am ashamed of my tears, and altogether there is something insufferable in my soul. I feel that I can no longer bear the sight of my lamp, of my books, of the shadows on the floor. I cannot bear the sound of the voices coming from the drawing-room....