Renaissance scientists also made significant advances
in the development of optical instruments. The period of
the late 16th and early 17th centuries is especially signifi-
cant as the time when the MICROSCOPEand the TELESCOPE
were invented. Equally of concern to scientists was the na-
ture of light and its mode of propagation. Two main theo-
ries had emerged in antiquity. Some considered that light
was emitted from the eye, the object, or both, and oper-
ated by traveling between the eye and the visible object.
Others, following Aristotle, denied that anything traveled
between eye and object, and argued instead that light was
a state of the medium acquired instantaneously from the
presence in it of a luminous object. Aristotle’s view found
wide acceptance among Renaissance scholars. If light did
travel, it was asked, why, unlike sound, was no interval
noted between the occurrence of an event and its percep-
tion? Against this view, supported by KEPLERand René
Descartes, scholars such as Francesco Maurolico (1494–
1575), in his posthumously published Photismi (1611),
argued that light emanated from the observed body and
traveled directly and rectilinearly to the eye of the ob-
server. It was not clear, however, where the image of the
object was formed. Traditionally it had been supposed that
the lens was the recipient of vision and that the lens was
placed in the center of the eye. The lens was first sited cor-
rectly by the anatomist Matteo Colombo (c. 1516–59),
while the retina was first proposed as the site of image for-
mation by Felix PLATTERin 1583. LEONARDO DA VINCIhad
earlier recorded how the image, as it formed on the retina,
became inverted, a phenomenon that was duly accounted
for by Kepler in his Ad Vitellionem (1604).
There remains the question of color and such related
phenomena as the rainbow and the prism. No one before
Isaac Newton (1672) suspected that white light was a
compound mixture of the primary colors. Aristotle had
thought, and in this he had been followed by all medieval
and Renaissance scholars, that white light was a simple
quality; color was produced by a weakening or modifica-
tion of light as it was reflected, refracted, or corrupted by
the medium. The rainbow, consequently, had been held to
be caused by reflection from the drops of water sited in a
conveniently placed cloud. Against this Maurolico argued
that the rainbow resulted from internal reflections within
the raindrop, while Kepler considered it to be due to both
internal reflections and refractions. Further progress in
this and other optical problems awaited a clearer under-
standing of the nature of light.
Further reading: David Park, The Fire Within the Eye
(Princeton, N.J.: Princeton Univesity Press, 1999); Arthur
Zajonc, Catching the Light: The Entwined History of Light
and Mind (Oxford, U.K.: Oxford University Press, 1995).
Oratorians See PHILIP NERI, ST
Orcagna (Andrea di Cione) (c. 1320–c. 1368) Italian
painter, sculptor, and architect
The son of a goldsmith, Orcagna (whose name was Flo-
rentine argot for “archangel”) was admitted to the guild of
painters in his native Florence in about 1343 and to the
guild of stonemasons nine years later. Inclined to paint in
a fashion that predated GIOTTO, Orcagna painted an altar-
piece in the Strozzi chapel of Sta. Maria Novella, Florence
(1354–57), which is now the only painting definitely at-
tributed to him. Probably also by him was the trilogy of
frescoes for the nave of Sta. Croce, Florence (c. 1350), and
the St. Matthew altarpiece (1367; Uffizi, Florence), which
was finished by his brother Jacopo di Cione (died 1398)
after Orcagna fell ill. His best-known sculptural work was
the ambitious tabernacle in Orsanmichele (1359). As an
architect he directed the construction of the cathedral in
Orvieto (1359–62) and also advised on the building of the
cathedral in Florence.
Further reading: Gert Kreytenberg and David Finn,
Orcagna’s Tabernacle in Orsanmichele, Florence (New York:
Harry N. Abrams, 1994).Ordóñez, Bartolomé (c. 1490–1520) Spanish sculptor
Born into a wealthy family in Burgos, Ordóñez studied in
Italy, probably under Andrea SANSOVINOin Florence, and
later imported many features of the High Renaissance into
his native Spain. While still in Italy, he produced a marble
relief, the Epiphany (c. 1516–18), for the Caracciolo
chapel in Naples, on which he worked with Diego de
SILOE, and the marble tomb of Andrea Bonifacio (c. 1518;
SS. Severino e Sosia, Naples). He then moved to Barcelona,
where he executed important wood and marble carvings
for the cathedral. In 1519 he was commissioned by
Charles V to produce the tomb for Philip the Handsome
and Joanna the Mad in the royal chapel in Granada cathe-
dral; when Ordóñez died the following year at Carrara,
where he was working on the monument, the commission
was almost completed. After his death his style was much
imitated, especially in Naples and Flanders.Oresme, Nicolas (c. 1320–1382) French mathematician
and physicist
Oresme, who was born at Caen, flourished under the pa-
tronage of Charles V of France, and after serving as tutor
to the future Charles VI he was appointed bishop of
Lisieux in 1377. In his most original work, De configura-
tionibus qualitatum (c. 1350), Oresme tried to show in the
inadequate mathematics of his day how changing “quali-
ties,” such as speed, could be handled geometrically. He
also, in his Livre du ciel et monde (c. 1377), a commentary
on Aristotle’s De caelo, considered the question of the
earth’s rotation. Despite appearing to have disposed of the
traditional objections to such a possibility, he affirmed,
nonetheless, his commitment to the PTOLEMAIC SYSTEM. In
a further work, the Algorismus proportionum, he intro-33448 8 OOrraattoorriiaannss