“They consider that they have given and taken from each other the most sacred pledges, and they may not break them and fall into enmity.”
Socrates depicts two lovers who regard their mutual promises as binding, even though their relationship follows the less philosophical path of his two possible outcomes. The line describes commitment within a particular ancient mythical account; it is not a free-standing promise that every relationship will remain harmonious.
Source details
Phaedrus, approximately Stephanus 256d–e, Socrates’s second speech contrasting the self-controlled philosophical lovers with another pair moved more by ambition and desire. Jowett English, Project Gutenberg #1636. The sentence belongs to the second pair, NOT the ideal self-controlled pair, which matters to its meaning; these are a philosophical narrator’s words, not a romantic pledge made by Plato.