THE MATERIAL FOR DEVELOPMENT	149
sixty-three graded colours, the beautiful coloured letters of the
alphabet lying in their compartments—all these are invitations
given by things.
The child obeys any object which at that moment corresponds
with his most acute need for action. In the same way in a field,
the petals of all the flowers are calling to other living things with
their perfumes and their colours, but the insects chooses the flower
which is made for him.
3.	Activity.   Another character of the material of develop-
ment is that it must lend itself to the activity of the child.   The
possibility of rousing the interest and attention of the child does
not depend so much on the quality of things as on the opportunities
which they offer for doing something with them.
That is, in order to make a thing interesting, it is not enough
that it should be interesting in itself, but it must lend itself to
the motor activity of the child. There must be, for instance,
small objects which can be moved from their places; it is then the
movements of the hand which pleases the child as he busily makes
and unmakes something, displaces and replaces things many times
in succession, thus making prolonged occupation possible. A very
beautiful toy, an attractive picture, a wonderful story, may doubt-
less rouse the interest of the child, but if the child may only look
and listen and touch an object which remains in its place, his
interest will be superficial and will pass from one object to another.
Hence the environment is all so planned that it lends itself to the
child's love of being active; it is beautiful, but that would interest
the child for only a single day, whilst the fact that every object
may be removed, used and put back in its place makes the attrac-
tions of the surroundings inexhaustible.
4.	The Limits.   Finally another principle common to all the
material means provided for education is the following, up till
now very little understood and yet of the very highest pedagogic
interest: the material must be limited in quantity.   This fact, once
stated, is logically clear to our understanding; the normal child
does not need stimuli to wake him up, to put him in connection