122 ECONOMIC ESSAYS IN HONOR OF JOHN BATES CLARK 
its own sake. It aims to understand present facts in regard to 
land ownership in all their human relationships, to explain ther 
development in the past, and to discover present tendencies of 
growth. As an art, it aims to frame constructive land policies 
for particular places and times. 
All our social sciences are a result of evolution characterized by 
growing complexity, differentiation and integration, to use terms 
which the student of Herbert Spencer will readily recognize. 
Many of the topies with which we deal in land economies had 
received discussion, and some of them elaborate discussion, before 
we ever heard of land economics. Likewise, before we had eco- 
nomics as a separate social science, we find discussion of eco- 
nomic questions, and 2000 years before the time of Adam Smith, 
Aristotle treated economic ideas in a way that even now is 
instructive. What land economists have done is to gather together 
scattered discussions of various topics relating to land as an 
economic concept; to separate them from other economic dis- 
cussions; to round them out; and to make thus a separate branch 
of economic science. 
The question of what is science is often raised and there can 
be no doubt that very many will be skeptical as to the possibility 
at the present time of a science of land economics. It is well, 
therefore, for the writer to state his position. To him science 
means generalized knowledge with certain metes and bounds 
determined by the particular field of knowledge. It deals with 
phenomena and their causes which are of such a kind that they 
are capable of being treated as a separate branch of knowledge 
These phenomena and their causes must have a certain magnitude 
to form a branch of knowledge. We may get together a small 
group of phenomena, a dozen or two, and consider their causes. 
Even if these were interesting and important, the field of knowl- 
edge would be too small for separate treatment. In economics 
we take human relationships of a particular kind in their eco- 
nomic aspects. These relationships multiply and fall into various 
distinct branches of economics. Some of these relationships of 
a particular kind may at first be too few really to form a 
separate branch, but they may increase, absolutely and relatively, 
and thus acquire the status of a separate branch of knowledge. 
This is true with respect to those relationships arising out of land 
as property. Take agriculture, for example. In the self-sufficing