How then does anybody ever 
manage to draw properly? One 
answer is that we are taught or 
teach ourselves. There is of 
course much truth in this. 
Leonardo taught the principles 
of perspective and methods for 
their utilization to his 
disciples, and art teachers have 
been doing the same ever since. 
We also pick up a good deal of 
information about the geometry 
of perspective informally, 
through trial and error and by 
looking at pictures.

    But another answer may be 
more important. There is a way 
in which we do perceive in 
accord with the two-
dimensional characteristics of 
the retinal image, which I 
referred to earlier as 
perception in the proximal 
mode. We do perceive railroad 
tracks and roads as converging, 
for instance, even while we 
perceive them as parallel, and 
we do perceive plates on a table 
as "elliptical," even while 
perceiving them as circular. 
Although constancy is our 
dominant mode of perception, 
the presence of the proximal 
mode, or the potential to focus 
on it, may play a major role in 
drawing. When faced with the 
task of drawing a road, for 
example, the presence of the 
proximal mode allows us to copy 
the percept in which the sides 
of the road converge rather 
than the usually dominant 
percept in which they are 
parallel.