Love
Love is present in many different forms in Eclipse. We see romantic love between Edward and Bella and between Edward and Jacob. We see familial love between the Cullens, and between Bella and her father.
Transformation
Eclipse shows us Bella and Edward grappling with the idea of turning Bella into a vampire, something that becomes imperative when the Volturi return and realize that Bella has not yet been transformed. Bella initially was attracted to the beauty and eternal youth that come with being a vampire, but she begins to hesitate when she realizes that she will lose her family, friends, identity, and maybe her strong physical love for Edward.
Jealousy
There is a lot of jealousy in Eclipse. Edward and Jacob are jealous of each other since they are rivals for Bella's love and attention. However, Jacob expresses his jealous frequently while Edward plays his closer to his chest to win Bella over. Additionally we also see jealousy between Bella and Rosalie. Bella is jealous of Rosalie's vampirism and beauty while Rosalie envies Bella's humanity because it means she can have children.
Mortality
Mortality is shown to have its pros and cons in Eclipse. For a human associating with supernatural creatures, mortality is dangerous because it makes you vulnerable and could cause you to lose your life. However immortality means you will outlive all the mortal friends and family you have, and it causes you to lose human abilities such as childbearing.
Possession
We see that Edward and Jacob both have a strong desire to possess Bella that drives them into competition with each other. We even see Jacob forcefully kiss Bella and then threaten to go fight with Victoria if she doesn't return his feelings. In these scenes, Jacob is being driven by his feelings to possess Bella above all else, and acts accordingly.
