I'm looking for textual references in Plato's dialogues where he discusses the difference between having and possessing with respect to actuality and potentiality. I would be grateful if anybody could help me with it.
I'm no Greek scholar, but Phaedrus is one work where possession is discussed in the context of love including the virtues of pederasty rooted in love. From WP:
Remarking that he is in the grip of something divine, and may soon be overtaken by the madness of the nymphs in this place, he goes on... The problem, he explains, is that one overcome with this desire will want to turn his boy into whatever is most pleasing to himself, rather than what is best for the boy... The boy's intellectual progress will be stifled, his physical condition will suffer, the lover will not wish the boy to mature and take a family, all because the lover is shaping him out of desire for pleasure rather than what is best. At some point, "right-minded reason" will take the place of "the madness of love", and the lover's oaths and promises to his boy will be broken.
This is possessive. There is a better way to approach relationships where one can have love, but not possess the lover. Again from WP:
Phaedrus believes that one of the greatest goods given is the relationship between lover and boy. This relationship brings guidance and love into the boy’s life. Because the boy has a lover as such a valuable role model, he is on his best behavior to not get caught in something shameful. To get caught in something shameful would be like letting down his lover, therefore the boy is consistently acting his best. The absence of shame makes room for a sense of pride to come in; pride from the wealthy feeling of impressing one's own lover. Impressing one's own lover brings more learning and guidance into the boy's life.
While pederasty is generally frowned on in the modern world, the lesson about the difference between an altruistic and possessive love would obtain to any sort of relationship.