ous _thoughts_ will not make his
body _act_ bravely. His legs may run away against his will to fight. The
physical instrument of his mind (his brain), and also certain associated
sets of muscles, must be sufficiently exercised in the _action_ of
courage to build up within him the _physical structure_ of fearlessness
that will be instantly responsive to a _mental attitude_ of bravery.

[Sidenote: Right Exercise for Development]

If for any reason the brain instrument is weak or undeveloped, it can
handle only weakly either in-coming messages to the ego from the senses,
or out-going impulses from the mind to the muscles. So, because of this
undeveloped brain instrument, the full capability of neither the inner
nor the outer man can be built up and put to use. Obviously, therefore,
if one is ambitious to succeed, he needs to know and to practice the
_coordinated mind-brain-muscle exercises_ that will increase the
quantity and better the quality of his man capacity. Since he is a
"many-minded, many-bodied" man, _general_ physical and mental exercise
will not develop the _particular_ qualities required to assure his
success. Each and every mind-brain-muscle set must be built up
individually by _specific_ exercises which strengthen _that particular
unit_ of the multiplex man. Then, of course, all his units should be
taught to work _together_ to make his success certain with his
all-around capability fully developed and coordinated.

[Sidenote: The Discriminative-Restrictive Method]

Luther Burbank worked out "discriminative-restrictive" methods of growth
that may be applied as successfully to men as to plants. He could not
have built up the ability of a prune tree to produce _delicious_ fruit
if he had not fed into the tree structure, or instrument of production,
a sufficient quantity and high quality of the _particular plant foods of
deliciousness_. He restricted his experimental prune trees to the
development of specific delicious qualities, by giving them no food
except that _discriminatively_ selected for his purpose. That is, he
made them develop in one way and in one way only, when he was making a
particular test.

Similarly, as has been stated before, you can develop the specific _man_
qualities you need to succeed. You must _feed_ to a particular mind
center, through the related brain center, _selected sense impressions_.
These can come only from the coordinated set of _muscles_ governed by
that mind-brain center