Saints Cosmas and Damian | Cosmas of Prague | Cosmas Indicopleustes | Cosmas Ndeti | Cosmas Damian Asam | Cosmas' | Cosmas |
Under the instruction of Cosmas, who also taught John's orphan friend (the future St. Cosmas of Maiuma), John is said to have made great advances in music, astronomy and theology, soon rivalling Pythagoras in arithmetic and Euclid in geometry.