How does Hurston reveal Nanny's motivation for forcing Janie to marry? Is that motivation pure, malevolent, or something in between in Their Eyes Were Watching God?
Nanny's motivation is out of love and concern for her granddaughter. It is not entirely pure, but it is certainly not malevolent.
When she sees "Johnny Taylor lacerating Janie with a kiss," Nanny calls Janie to her and takes action. She tells Janie that she is a woman now; further, she explains to Janie that she is now old and she wants Janie married so that she will be protected from harm. She explains that she does not want Janie to go the way of her mother, who became wild and ran away. In her frustration and worry, she slaps Janie, but then she weeps with Janie. She tells Janie that she would not hurt Janie for any reason; she is just so worried that Janie will act irresponsibly upon her sexual urges. Nanny rocks with Janie in her arms, saddened that Janie has begun to mature, and worried for her safety.
"'Tain't Login Killicks Ah wants you to have, baby, it's protection. Ah ain't gittin' ole, honey....Mah daily prayer now is tuh let dese golden moments rolls a few days longer till Ah see you safe in life."
Her grandmother tells Janie both her personal history and that of her mother. Because they were both abused by men, Nanny wants to protect her granddaughter and ensure that nothing like hers and her daughter's experiences happen. Her motivation is good, but the arrangement with the older man, Logan Killicks, is not wise because, while he may be able to protect Janie, he is too old to relate well to Janie and too old for Janie to love.