Peter Paul Rubens presented his Venus in Front of the Mirror as the ultimate symbol of beauty. She is aware of the viewer in a mirror that frames her face like a portrait. Great play is made of the sensual reproduction of her skin and silky hair, which is further enlivened by the contrast with the dark-skinned maidservant. The few costly accessories, otherwise decorative additions to elaborate clothing, emphasize the figure’s nakedness.
The sensual qualities of the painting are created by Rubens’s subtle painterly approach. He alternates sketchy brushstrokes, drawn over the ground like a transparent veil, with compact areas, painted in great detail. One particularly attractive feature of the picture is the contrast between the goddess’s encounter with the viewer, which seems to occur almost by chance, and the representation of her beauty, as if conceived for a spectator. The mirror that Cupid holds up for the goddess reveals an additional level of meaning: the reflection of Venus, which reveals her beauty to the viewer, becomes a symbol of painting that competes with nature to produce an image that is as real as possible. Rubens modelled his work on compositions by Titian and Veronese that combine Venus and a mirror, and probably also offered this possible interpretation.
(http://www.liechtensteincollections.at/en/pages/artbase_main.asp?module=browse&action=m_work&sid=87294&oid=W-1472004121953420224)