Also at this point a query arises, irrelevant indeed, but hardly to be
suppressed: "Why are we so profoundly moved by forms related in a
particular way?" The question is extremely interesting, but irrelevant
to aesthetics. In pure aesthetics we have only to consider our emotion
and its object: for the purposes of aesthetics we have no right, neither
is there any necessity, to pry behind the object into the state of mind
of him who made it. Later, I shall attempt to answer the question; for
by so doing I may be able to develop my theory of the relation of art to
life. I shall not, however, be under the delusion that I am rounding off
my theory of aesthetics. For a discussion of aesthetics, it need be
agreed only that forms arranged and combined according to certain
unknown and mysterious laws do move us in a particular way, and that it
is the business of an artist so to combine and arrange them that they
shall move us. These moving combinations and arrangements I have called,
for the sake of convenience and for a reason that will appear later,
"Significant Form."

A third interruption has to be met. "Are you forgetting about colour?"
someone inquires. Certainly not; my term "significant form" included
combinations of lines and of colours. The distinction between form and
colour is an unreal one; you cannot conceive a colourless line or a
colourless space; neither can you conceive a formless relation of
colours. In a black and white drawing the spaces are all white and all
are bounded by black lines; in most oil paintings the spaces are
multi-coloured and so are the boundaries; you cannot imagine a boundary
line without any content, or a content without a boundary line.
Therefore, when I speak of significant form, I mean a combination of
lines and colours (counting white and black as colours) that moves me
aesthetically.