The School of Athens
(Raphael (Raffaello Sanzio), School of Athens, 1509, Stanza della Segnatura, Pontifical Palace, Rome)
"The painting celebrates classical thought, but it is also dedicated to the liberal arts, symbolized by the statues of Apollo and Minerva. Grammar, Arithmetic and Music are personified by figures located in the foreground, at left. Geometry and Astronomy are personified by the figures in the foreground, at right. Behind them stand characters representing Rhetoric and Dialectic. Some of the ancient philosophers bear the features of Raphael's contemporaries. Bramante is shown as Euclid (in the foreground, at right, leaning over a tablet and holding a compass). Leonardo [Leonardo da Vinci (1452-1519)] is, as we said, probably shown as Plato. Francesco Maria Della Rovere appears once again near Bramante, dressed in white. Michelangelo, sitting on the stairs and leaning on a block of marble, is represented as Heraclitus. A close examination of the intonaco shows that Heraclitus was the last figure painted when the fresco was completed, in 1511. The allusion to Michelangelo is probably a gesture of homage to the artist, who had recently unveiled the frescoes of the Sistine Ceiling. Raphael - at the extreme right, with a dark hat - and his friend, Sodoma, are also present (they exemplify the glorification of the fine arts and they are posed on the same level as the liberal arts)."
www.kfki.hu/.../r/ raphael/4stanze/1segnatu/1/
1) Plato and Aristotle

Plato (left) is carrying a copy of his Timeus, and pointing upwards, which symbolizes his concern with the eternal and immutable Forms. Aristotle (right) is carrying a copy of his (Nicomachean) Ethics, and keeping his hand down, which symbolizes his concern with the temporal and mutable world.
(The other interpretation is that Raphael was an early basketball fan, and that the Vatican carefully removed the spinning basketball from Plato and the bouncing basketball from Aristotle).
(2) Pythagoras (crouching with book) and Parmenides (standing with book)

(3) Heraclitus (with Michelangelo's features)

(4) Euclid

(5) Zoroaster (facing, with beard) and Ptolemy (back to us, globe) and Raphael (dark hair, facing)
