According to Platos myth of creation, originally everyone was
once half of a sphere. The two halves of the sphere either consisted of a male
half linked with another male half, a female half linked with a female half, or
male/female or female/male divisions.
Upon birth, thought Plato, the sphere is split in two, and the divided parts were thrown into the world, thus explaining the phenomenon of human sexual attraction.
As he looks over the girls in the classroom, his mind wanders, and he wonders how his beloved looked at that youthful age.
The poem is also about labor, referring to Adams curse of having to earn his livelihood and Eves curse of having to endure the pain of childbirth. He also despairs at the length of the learning process.