The marble reliefs depicting Sculpture and Painting are by Andrea Pisano (1348-1350), while those representing Grammar, Dialectic, Music, Geometry and Arithmetic, and Astrology (or Harmony) were carved by Luca della Robbia between 1437 and 1439. The reliefs dedicated to Sculpture and Painting were originally on the eastern side of the Campanile, next to the relief depicting Architecture, forming a set showing the three figurative arts. And it is to art, defined by Dante as “God’s grandchild”, that these last medieval reliefs are dedicated. The figure in the relief showing Sculpture is traditionally identified as Phidias, the famous Athenian sculptor, here portrayed in the act of sculpting a statue. The Greek painter Apelles, shown in a medieval setting, is traditionally held to represent Painting. The 15th century reliefs depict the liberal arts or humanities taught in medieval universities. They are represented by characters from classical antiquity held to have excelled in their fields, whose writings were known to the scholars of the Quattrocento. Grammar shows either Aelius Donatus, a Roman grammarian who lived in the 4th century AD, or possibly Priscian, as he lectures. Dialectics depicts the Greek philosophers Plato and Aristotle, who lived between the fourth and fifth centuries BC, engaged in an animated discussion. Music is represented by Orpheus, a character from classical mythology, playing the lute and taming the savage beasts around him; while Geometry and Arithmetic are personified by Euclid, a Greek mathematician who lived in the 4th century BC and Pythagoras, Greek philosopher and scientist who lived in the 6th century BC, here shown in debate. The figure represented in Astrology is traditionally identified as Pythagoras, one of the fathers of this science.