“Why does a fine sketch please us more than a fine picture? It is because there is more life in it and fewer forms …Why can a young student, incapable of doing even a mediocre picture,do a marvelous sketch? It is because the sketch is the product of enthusiasm and inspiration, while the picture is the product  of labour, patience, lengthy study and consummate experience in art.”
from, The Salon of 1767 by Denis Diderot
from, A Miscellany of Artist’s Wisdom, compiled by Diana Craig