The play shows the error of adhering in an exaggerated and pretentious way to social conventions that hamper living. When Elena Popova's husband dies, she decides to take on the nineteenth-century, middle-class social convention of a long period of mourning for her husband. She decides she must be faithful to his memory—even though he cheated on her with other women when he was alive—and never remarry or invite in the love of another man.

When the play opens, Popova has not left the house for seven months. Her pragmatic working-class servant, Luka, rightly thinks this is ridiculous and tries to tell her so. At this moment, Grigorii Smirnov arrives, telling Elena she owes him 1,200 roubles that he needs now to pay his mortgage the next day. When she informs him that she won't have the money for two days, they get into a fight, with Elena insulting Grigory by calling him a bear. This leads to the two deciding to fight a duel, with Elena now taking on an exaggeratedly macho male role. The play is a comedy, and the two main characters kiss and realize they are in love before any harm can be done.

The play drives home the point that lives can be wrecked because of overwrought notions of duty and honor. The play's message is that people need to live and love, not get caught up in trying to adhere to exaggerated and stifling standards of behavior.

I would argue that the central theme in The Bear is the prevailing nature of happiness and its victory over grief. Other themes include joy and new beginnings.

Elena Popova has lost her husband, and seven months later, she is still refusing to leave the house. Her mourning is interrupted by the arrival of Gregorii Smirnov, who ignores Elena's pleas to be left alone and demands to be paid back money that was owed to him by Elena's late husband. In order to get rid of him, she tells him to come back in two days. Gregorii, however, is not to be deterred and refuses to leave until he has got his money.

The argument escalates, to the point that Gregorii challenges Elena, an ardent feminist, to a duel. She accepts, and he sets about instructing her on how to use a pistol, so as to ensure a fair fight. He gradually realizes that he is falling in love with this obstinate widow and that her tenacity and refusal to back down from a challenge are extremely appealing.

After refusing his proposal of marriage several times, Elena accepts a passionate kiss from Gregorii, which tells us that he has snapped her out of her stupor of grief and reintroduced her to the delights of living. Happiness and love, therefore, have prevailed over grief.

Here, as elsewhere in Chekhov's works, the pretensions of the bourgeoisie in Tsarist Russia are much in evidence. In this hidebound society, where etiquette and "correct" standards of behavior are to be observed at all times, people are effectively encouraged to hide their true selves behind a mask. As well as leading to misunderstanding, as it does in "The Bear," it can also thwart an individual's happiness.

Both negative consequences are on display in "The Bear." Smirnov has powerful feelings for Popova but is unwilling to show them, as he remains trapped in the conventions of his social class. When he rocks up at Popova's place, he's there on a business errand; he seeks to recover the large sum of money owed to him by Popova's recently deceased husband. But this serves to conceal Smirnov's amorous feelings for Popova, which remain unexpressed until right near the very end of the play.

For her part, Popova feels the need to behave in the way befitting a gentleman rather than a lady by agreeing to participate in a duel with Smirnov. This isn't who she really is; she's a woman of refinement, a gentlewoman. But because of the onerous demands that this unpleasant situation has imposed upon her, she agrees to accept Smirnov's bizarre challenge. She, like “The Bear,” is unable to communicate her true feelings, due to established social convention.

The theme of The Bear is that life is meant to be lived.

The play is a farce in one act.  Life, after all, is funny!  Elena, a wealthy widow, lives alone because she wants to honor her memory.  She has only Luka, her aged footman.  She has vowed to neither leave the house nor accept visitors.

I shall never go out.... Why should I? My life is already at an end. He is in his grave, and I have buried myself between four walls.... We are both dead.

Luka strongly disagrees.  He thinks that his mistress should leave the house, or at least have neighbors over.  Mourning this way is not living, he insists.

You've forgotten all your neighbours. You don't go anywhere, and you see nobody. We live, so to speak, like spiders, and never see the light. 

Then a brusque visitor, Smirnov, arrives who will not take no for an answer when he is told she will not receive visitors.  He insists that her late husband owes him money, and he will stay until it is paid up.  At first he is polite, but when she says she has to wait for the money to arrive he gets blusteringly angry.

Smirnov’s presence turns out to be just what Elena needs.  He is just rude enough to get her attention, and his insistence that women cannot love annoys her.

Men are faithful and constant in love! What an idea!

In the end, Smirnov gets so frustrated with her that he challenges her to a duel—even though she’s a woman—and then he realizes he has fallen in love with her.

Although the play is full of silliness and slapstick, there is a serious theme here. Chekhov is reminding us that life is for living.  When Elena finally lets Smirnov in, she comes to life.  She admits that the husband she is being so faitful to was not even faithful to her.  He left her nothing, not even the money, because the money was hers!