Samuel Taylor Coleridge is a reflective poet and devoted father who serves as the speaker of the poem. Raised in a bustling, restrictive city and educated in dim cloisters, he harbors a deep, spiritual longing for the natural world. He spends his quiet, sleepless hours meditating on his past and formulating an educational philosophy for his infant child. His observations of the fluttering ash in his fireplace prompt thoughts on how humanity reflects the divine.

Hartley Coleridge is the speaker's 17-month-old son, affectionately described as a slumbrous, cradled infant. His gentle breathing provides the only rhythmic sound in the otherwise completely silent winter cottage. He embodies untainted potential and stands to inherit the vast, natural education his father was denied in his own youth. The speaker views Hartley as a blank slate who will learn the eternal language of the earth.

The Sister is the speaker's beloved sibling and early playmate. She appears in his childhood memories from a time when they were young enough to be dressed in identical clothing. Her imagined face is a comforting sight the young speaker longs to see when the schoolhouse door opens. She brings a sense of familial warmth to his cold educational environment.

The Stern Preceptor is a strict, imposing teacher at the speaker's childhood school. His rigid authority forces the young poet to feign attention to his reading book while secretly daydreaming about his rural birthplace. He represents the oppressive nature of formal, indoor education that the speaker hopes his son will avoid.

God is conceptualized as the Great Universal Teacher who reveals his teachings through the shapes and sounds of the physical environment. Instead of utilizing traditional religious structures, he uses lakes, mountains, and the changing seasons to instruct and mold the human spirit. The speaker trusts this divine presence to provide his son with a continuous, gentle education.