When man learned to domesticate animals he made a great step forward
and entered what is known as the _pastoral_ period, in which his chief
occupation was the care of flocks and herds. This contributed much to
his material support and quickened his social and intellectual
movement. After a time, when he remained in one place a sufficient
time to harvest a short crop, he began agriculture in a tentative way,
while his chief concern was yet with flocks and herds. He soon became
permanently settled, and learned more fully the art of agriculture, and
then entered the permanent _agricultural_ stage. It was during this
period that he made the most rapid advances in {39} the industrial arts
and in social order. This led to more densely populated communities,
with permanent homes and the necessary development of law and
government.

As the products of industry increased men began to exchange "the
relatively superfluous for the relatively necessary," and trade in the
form of barter became a permanent custom. This led to the use of money
and a more extended system of exchange, and man entered the
_commercial_ era. This gave him a wider intercourse with surrounding
tribes and nations, and brought about a greater diversity of ideas.
The excessive demand for exchangeable goods, the accumulation of
wealth, and the enlarged capacity for enjoyment centred the activities
of life in industry, and man entered the _industrial_ stage. At first
he employed hand power for manufacturing goods, but soon he changed to
power manufacture, brought about by discovery and invention. Water and
steam were now applied to turn machinery, and the new conditions of
production changed the whole industrial life. A revolution in
industrial society caused an immediate shifting of social life.
Classes of laborers in the great industrial army became prominent, and
production was carried on in a gigantic way. We are still in this
industrial world, and as electricity comes to the aid of steam we may
be prepared for even greater changes in the future than we have
witnessed in the past.[1]

In thus presenting the course of civilization by the different periods
of economic life, we must keep the mind free from conventional ideas.
For, while the general course of economic progress is well indicated,
there was a slow blending of each period into the succeeding one.
There is no formal procedure in the progress of man. Yet we might
infer from the way in