Saint Gregory and the holy spirit in the form of a dove

The title tells you to look for the dove, and that bird is the whole point of the picture. Gregory was pope in Rome around the year 600, and the way he came to be painted goes back to an early life of him. While he dictated his commentary on the prophet Ezekiel, a curtain hid him from his secretary, and during the long silences the man peered through a gap and saw a dove settled at the pope's head, its beak close to his lips. From then on painters marked Gregory out by setting that bird at his ear, the Holy Spirit handing him the words. Working in Italy in the 1630s, Stom keeps the dove right against the saint's face, so no one could take him for anyone else.