a collection of individuals with
the same habits is what we call a _group_. The first condition, then,
for the study of a habit is the determination of the group which has
practised it. At this point we must beware of the first impulse; it
leads to a negligence which may ruin the whole of our historical
construction.

The natural tendency is to conceive the human group on the model of the
zoological species--as a body of men who all resemble each other. We
take a group united by a very obvious common characteristic, a nation
united by a common official government (Romans, English, French), a
people speaking the same language (Greeks, ancient Germans), and we
proceed as if all the members of this group resembled each other at
every point and had the same usages.

As a matter of fact, no real group, not even a centralised society, is a
homogeneous whole. For a great part of human activity--language, art,
science, religion, economic interests--the group is constantly
fluctuating. What are we to understand by the group of those who speak
Greek, the Christian group, the group of modern science? And even those
groups to which some precision is given by an official organisation,
States and Churches, are but superficial unities composed of
heterogeneous elements. The English nation comprises Welsh, Scotch, and
Irish; the Catholic Church is composed of adherents scattered over the
whole world, and differing in everything but religion. There is no
group whose members have the same habits in every respect. The same man
is at the same time a member of several groups, and in each group he has
companions who differ from those he has in the others. A French Canadian
belongs to the British Empire, the Catholic Church, the group of
French-speaking people. Thus the different groups overlap each other in
a way that makes it impossible to divide humanity into sharply distinct
societies existing side by side.

In historical documents we find the contemporary names of groups, many
of them resting on mere superficial resemblances. It must be made a rule
not to adopt popular notions of this kind without criticising them. We
must accurately determine the nature and extent of the group, asking: Of
what men was it composed? What bond united them? What habits had they in
common? In what species of activity did they differ? Not till after such
criticism shall we be able to tell what are the habits in respect of
which the group in question may be