The apparent randomness of the picture's point of view, privileging the bystanders over the main plot, informs other parts of the picture, too. The figure of Christ in Andrea Mantegna's Christ Entering Limbo, perhaps the period's most well known Rückenfigur, simply responds to the logic of the picture's orientation and probes no investigation into Christ's motives. Alberti had recommended the fifteenth-century painter to make his work respond to a spectator in front of it, defining the artwork as a composition oriented outwards, towards the viewer. It seems as if Masaccio and Leonardo did not place their figures in space after they had constructed the space of their pictures; they rather organized perspective around the figures, not as a means to represent space but as a way to divide the picture between important and subordinate parts. The art of carpentry was as much a scienzia as the art of mathematics.