Indiana's number herms, like their classical counterparts, mark terratorial boundaries and milestones. The number four has historically been associated with the Greek god Hermes's birth, which is described in classical literature as occurring on the fourth day of the month. According to Susan Ryan, Indiana relates the number four with the allegorical theme of the Ten Ages of Man, the fourth stage of which is adolescence, something the artist has called "the most dangerous time of life" (quoted in S.E. Ryan, Robert Indiana: Figures of Speech, New Haven, 2000, pp. 68 and 276). Four conveys its verbal and visual messages through the repetition of the number and the circle forms, as well as the word "four" itself which appears at the bottom. There is a comforting consistency about the stated and implied numerology: four fours, four sides to the wood panel and to the squares themselves and four spokes in the wheel.