Aristotle

Here Stephen is contemplating Aristotle's theory of light and colour, which is found in two of Aristotle's works: On the Soul and Sense and Sensibilia.

From Dante’s Inferno (4:130-131), meaning “master of those that know.” "Vidi il Maestro di color che sanno | Seder tra filosofica famiglia" - "I saw the master of those that know, | seated amid the philosophic family" Dante frequently acknowledges his debt to Aristotle whom he calls Maestro / Master and from whose writings and teachings Dante has based much of his works on. http://goo.gl/tGq4OB It is said that the play on the Italian use of ‘color’ and the English ‘colour’, is a connection that Joyce intended.

From Dante’s Inferno (4:131), meaning “master of those that know.”