All Art is Interpretation, and Sometimes It Makes Fools of Us

From a Fodor's miniguide

English: Michelangelo's David (original statue) Deutsch: David von Michelangelo (Original aus der "Accademia" in Florenz) Nederlands: David van Michelangelo (het originele beeld) (Photo credit: Wikipedia)

"As Michelangelo well knew, the Renaissance painting

 and sculpture that preceded his work were deeply

 concerned with ideal form. Perfection of proportion

 was the ever-sought Holy Grail; during the Renaissance, ideal proportion was

 equated with ideal beauty, and ideal beauty was equated

 with spiritual perfection. But David, despite its

 supremely calm and dignified pose, departs from these

 ideals. Michelangelo did not give the statue perfect

 proportions. The head is slightly too large for the

 body, the arms are too large for the torso,and the hands are

 dramatically large for the arms. The facade of the

 Duomo and was intended to be seen from below

 at a distance. Michelangelo knew exactly what he was

 doing, calculating that the perspective of the viewer

 would be such that, in order for the statue to appear

 properly proportioned, the upper body, head and arms

 would have to be bigger,as they are farther away

 from the viewer's line of vision. But he also did it

 to express and embody, as powerfully as possible

 in a single figure, an entire biblical story.

 David's hands are  big, but so was Goliath,

 and these are the hands that slew him."

English: Michelangelo's Pietà in St. Peter's Basilica in the Vatican. Français : La Pietà de Michel-Ange située dans la Basilique Saint-Pierre, au Vatican. (Photo credit: Wikipedia)

From a Renaissance website

An examination of each figure reveals that their proportions are not entirely natural in relation to the other.  Although their heads are proportional, the Virgin’s body is larger than Christ’s body.  She appears so large that if she stood up, she would likely tower over her son.  The reason Michelangelo did this was probably because it was necessary so that the Virgin could support her son on her lap; had her body been smaller, it might have been very difficult or awkward for her to have held an adult male as gracefully as she does.