Why does Sofia leave Harpo in The Color Purple?

Sofia leaves Harpo because he starts to beat her. In another sense, she leaves him because he has been influenced by his father to feel a need to physically dominate his wife, which is at odds with his natural inclination to be loving and submissive. Even though Harpo loves Sofia, he feels emasculated by her, and becomes consumed with the idea of making her "mind," like Celie "minds" Mister.

In fact, it is Celie herself who finally tells Harpo to beat Sofia. Celie's advice comes in a moment of spite: even though she is proud that Sofia is so much more independent than she is, she also resents it. Celie projects her own suffering at the hands of Mister onto Harpo and Sofia.

This toxic masculinity is a recurring theme in the book. Sofia and Harpo get into tremendous fights over this, which Sofia usually wins because of her greater size and strength. This inversion of gender roles, in which the woman is physically superior to the man, is another reason for Harpo's dissatisfaction.

Ultimately, Sophia leaves because Harpo has lost her respect. Sophia never doubts her own rebellious nature, and for Harpo to fall under the influence of his father in this way is an unforgivable sign of weakness.

Why do Sofia and Harpo argue in The Color Purple?

There is a major conflict between Sofia and Harpo, two characters in Alice Walker's novel The Color Purple. What is the cause of this conflict?

First, let's establish the relationship between these two. Relatively early in the novel Harpo meets and falls in love with Sofia. After she becomes pregnant, they get married; they have several other children in quick succession. But they won't stay a couple for very long: Harpo wants to dominate Sofia, but Sofia refuses to be dominated. Their arguments get physical, and she ultimately moves out with the children. Here, another character describes their fighting:

fighting like two mens. Every piece of furniture they got is turned over. Every plate look like it broke. The looking glass hang crooked, the curtains torn. The bed look like the stuffing pulled out. They don’t notice. They fight. He try to slap her. What he do that for? She reach down and grab a piece of stove wood and whack him cross the eyes. He punch her in the stomach, she double over groaning but come up with both hands lock right under his privates. He roll on the floor. He grab her dress tail and pull. She stand there in her slip. She never blink a eye. He jump up to put a hammer lock under her chin, she throw him over her back. He fall bam up gainst the stove. 

What causes this kind of fighting? Sofia isn't like a lot of other women of the day: she is assertive by nature, refuses to work as a maid, and wants equality with her husband. She is not afraid of men, and she's not shy about defending herself either; she's willing to fight to protect her own rights.

Harpo, meanwhile, is an otherwise kind man, but he is frustrated because he can't control Sofia or make her "mind." Maybe, Walker suggests, Harpo doesn't want to control his wife as much as he wants to live up to socially imposed standards for how men and women should behave:

Harpo want to know what to do to make Sofia mind. He sit out on the porch with Mr.——. He say, I tell her one thing, she do another. Never do what I say. Always backtalk.

To tell the truth, he sound a little proud of this to me.

Long story short, it is both the natural personalities of these two characters and the social expectations for each of them that causes the conflict between Sofia and Harpo.

How does Harpo know Sofia isn't coming back?

Harpo and Sophia are, perhaps, the couple most truly in love in Alice Walker's The Color Purple.  They are also the two characters who most exhibit swapping gender roles in a traditional relationship.  Harpo and Sophia were happily married until Harpo, after years of watching his father abuse Celie in every possible way, began questioning why Sophia didn't "mind" him the way Celie did Albert.  Celie, motivated by a jealousy that she grew to regret bitterly and later repent of, advised Harpo to beat Sophia into submission. Sophia, however, had made a pledge to herself years before that she would not accept such abuse, and she fights back. By Letter 32, Sophia has been gone from the home she shared with Harpo and the children for six months.  Harpo is openly distraught during this time and begins to assert his manhood and his independence by seeing other women. Finally, he and a friend convert the home he once shared with Sophia into a juke joint, and when Celie asks him what Sophia will think about this when she comes back, Harpo tells her that he knows now that she won't be returning.