The notion of causality puts new meaning into our view of the _training_
of a child. The doctrine of development puts new meaning into our notion
of the _nature_ of a child. We can understand man only when we view him
genetically, that is, in the light of his origin. We can understand a
child only in the light of what his ancestors have been.

As these lines are being written, the greatest, the bloodiest war of
history is in progress. Men are killing men by thousands and hundreds of
thousands. How can we explain such actions? Observation of children
shows that they are selfish, envious, and quarrelsome. They will fight
and steal until they are taught not to do such things. How can we
understand this? There is no way of understanding such actions until we
come to see that the children and men of to-day are such as they are
because of their ancestors. It has been only a few generations,
relatively speaking, since our ancestors were naked savages, killing
their enemies and eating their enemies' bodies. The civilized life of
our ancestors covers a period of only a few hundred years. The
pre-civilized life of our ancestors goes back probably thousands and
thousands of years. In the relatively short period of civilization, our
real, original nature has been little changed, perhaps none at all. The
modern man is, at heart, the same old man of the woods.

The improvements of civilization form what is called a social heritage,
which must be impressed upon the original nature of each individual in
order to have any effect. Every child has to learn to speak, to write,
to dress, to eat with knife and fork; he must learn the various social
customs, and to act morally as older people dictate. The child is by
nature bad, in the sense that the nature which he inherits from the past
fits him better for the original kind of life which man used to live
than it does for the kind of life which we are trying to live now. This