In his prologue, Longus describes finding a beautiful painting while walking in a grove, a painting lovelier than the grove itself. Longus writes:

Women giving birth, others dressing the babies, babies exposed, animals suckling them, shepherds adopting them, young people pledging love, a pirates’ raid, an enemy attack...

This painting raises in Longus the desire to describe it in writing. To depict a work of art in literature is called ekphrasis. The theme or message behind Longus's work of ekphrasis is to point to art itself: the novel, like the painting that inspires it, is a work of artifice. It is not what life is but what we might like it to be. It is meant, Longus writes:

as something for mankind to possess and enjoy ... [to] comfort the distressed, stir the memory of those who have loved, and educate those who haven’t.

The novel explores the themes of innocence and eros (erotic desire). Daphnis and Chloe's innocence is emphasized by their ignorance about their upper class births and through their lives sheltered from sophisticated urbanity living close to nature as rural shepherds in an idyllic setting. They are pictured as children of nature, and much of the novel's comedy comes from their innocence about love and lovemaking. They are depicted too as purer than most in their love because of their innocence.

The theme of eros or erotic desire is expressed through the importance of physical lovemaking. When the young couple tell the cowherd Philetas about the pain they are feeling, he informs them:

There is no medicine for Love, no potion, no drug, no spell to mutter, except a kiss and an embrace and lying down together with naked bodies.

The novel bluntly opines that their can be no relief until love is consummated. Love of soul must be joined to love of body.

Finally, class enters into the picture. Part of Longus's message or theme is that Daphnis and Chloe are meant for each other because, even though they are ignorant of it, they both come from the same upper class background. It seems they are fated for one another. Longus, thus, is not using the pastoral or ekphrastic forms to challenge the social order, but to affirm it.