in this painting, for example, by caravaggio, the idea of volume and the idea of mass-- we are dealing with density, with weight. these figures are solid. these figures have a sense of corporeality. they're tangible. and that is achieved through the illusionary techniques that are available to the artist. this i will cover a little further in the program today. what about line? now, line is a very important element of style. line can be used in so very many different ways. it can be obvious. it can be actual. in other words, as in this drawing, watercolor, we can see actual lines. they vary. you have thin lines. you have very thick lines. for example, the figures here have very agitated and excited lines. these are very straight lines. but they create the illusion and suggest volume. they suggest shape and form. line can also be implied, and that takes practice. it takes a considerable amount of work in order to be able to discern the implied lines because they're not actually drawn on the painting. they're not included there, and they're not easily discernible. the implied line, for e