Piero della Francesca seems to have been another incorruptible, though little is known about him: his birth date could have been any time between 1400 and 1420, though we know he died in 1492. His father was a tanner and his own first job was to paint the striped poles used to carry candles in religious processions. Yet such was the upwards mobility of the times, intellectual as well as social, that he made himself a master mathematician and played a bigger role in the spread of Euclid's geometry than anyone else. He wrote a number of learned treatises, three of which survive, including an exposition of the rules of perspective, De prospectiva pingendi, which demanded more mathematical skills than most painters have ever possessed.
Perspective and geometry figure both prominently and subtly in all Piero's works. He liked to organise large, plain masses of colour in patterns which suggest an underlying geometrical scheme. That gives his paintings the unfinished look which moderns like. He made a positive virtue of the light palette which the use of old painting methods forced on artists. There are always large areas of white or near-white in his works, the skies are big, light and sunny, and this pleasing radiance, combined with the absence of meticulous clutter, makes his paintings enormously attractive to our eyes. All this was carefully considered and deliberate. If we compare the two sections of altarpieces in the National Gallery, London The Baptism of Christ, and The Nativity the light tone colour scheme is the same in both, though for the first he used egg tempera and for the second oils (both are on panels of poplar). His Saint Michael, in the same gallery, is also light toned and the saint is framed by his white wings and a white marble balcony. Yet this is an oil painting too.
Piero always, as it were, goes against the grain of expectation. He never seems to have belonged to a workshop and travelled over a large part of Italy, a freelance, perhaps a lonely figure. He made no attempt to please his contemporaries by doing what they expected. In The Baptism of Christ, attention is likely to centre on the unknown background man taking his shirt off, a beautiful piece of painting which has no point other than the love of fine design, or on the angels gazing suspiciously at the near naked Christ. In the Nativity, the Christ child is insignificant compared with the chorus and orchestra above him, and their male conductor. In the Resurrection, set in Piero's home town of Sansepolcro, Christ emerges somnambulistically from a sarcophagus against which the sleeping guards lie - a strange and disturbing image. In his finest work, the wonderfully light and sparkling Flagellation in the Ducal Palace, Urbino, Christ and his tormentors have been pushed into the background, while three unrelated figures, who are not even watching the scourging, dominate the scene.
From: A New History, by Paul Johnson