s with these concrete things that you should
concern yourself mainly. The science of painting consists in the
knowledge of how to be the master of all the practical means of the
craft. For it is with these that you must work, with these you must
express yourself. These are the tools of your trade. They are the
words of your art language--the language itself being the abstract
elements--and the thoughts, the combinations which you may conceive in
your brain by means of these abstract elements.

You must have absolute command of these _materials_ of painting. No
matter how ideal your thought may be, no matter how fine your feeling
for line and color and composition, if you do not know how to handle
the gross material which is the only medium by which this can all be
made visible and recognizable to another person, you will fail of
either expressing yourself, or of representing anything else.

Now you will see what I have been driving at all this time; why I
have been talking in terms which may well be called not practical. I
want to fix your attention on the fact that there are two qualities in
a picture: that one will be always within you, mainly, and will
control the character of your picture, because it will be the
expression of your mental self; and the other the practical part,
which any one may, and all painters must learn, because it is the only
means of getting the first into existence.

The one, the abstract part, no one can tell you how to cultivate nor
how to use. If I tried to do so, it would be my idea and not yours
which would result. I can only tell you that it is the _thought of
art_, and you must think your own thoughts.

But the other, the material, the concrete, the practical, it is the
purpose of this whole book to help you to understand and to acquire
the mastery of, so far as may be done by words.

Teaching by words is difficult, and never completely satisfactory. But
much may be done. If you will use your own brains, so that what does
not seem clear at first may come to have a meaning because of your
thinking about it, we may accomplish a great deal. I cannot make you
paint. I cannot make you understand. I can give you the principles,
but you must apply them and think them out.

Everything I say must be in a measure general; for the needs of every
one are individual, and the requirement of each technical problem is
individual. I must speak for all, and not to any one. Yet I shall
state princi